Heated Topics - Why we can Never Agree

Disclaimer: This is just what I've noticed when people try to argue the most heated topics on this site. I am not stating my position on either topic, simply putting forth my understanding of the arguments for both sides and why the arguments remain, instead of being solved. You are welcome to put your own opinion in the comments, and clear up any mistakes I might have made with the arguments/parts I left out. I have tried to make this as unbiased as possible, please forgive me for any unintentional bias.

All of the most heated arguments on this site seem to have one thing in common: we can never agree because our definitions of right and wrong are drastically different, and neither of us wants to compromise, because that would mean letting some kind of great evil happen.
For example, the argument of Abortion, whether it's right or wrong/should be allowed or not. From my experience, pro-lifers believe that an unborn baby is just as alive and human as a born baby is, and therefore their lives should be treated with the same respect as a born baby's life. Killing it (which is what abortion does, in the eyes of a pro-lifer) is akin to murder, and therefore abortion should not be legal.
Pro-choicers seem to believe that the unborn fetus is not a human yet, and therefore still a part of the mother's body. Most seem to believe that a woman can do whatever she wants to her body, including removing a fetus from it, because it is her body, and therefore, her property to do with as she wishes. Abortion, then, should be allowed because if it isn't, it infringes on a woman's right to personal autonomy, and she'll either go to back-alley abortion clinics instead (which are very dangerous) or be forced to care for an unwanted baby.
The "tough cases" (i.e. rape, incest, threatening the mother's life, etc.)  are interesting, in terms of who supports them as an exception, where abortion is allowed, who supports them as tragic reasons that abortion should be available to everyone, or who says that "no matter what" abortions should not be allowed.
Some say that abortions should be available to every woman, and that the tough cases are extra-incentive for the nation to support that right. Some say that abortion for "personal and social convenience" is wrong because it is preventable by means of sexual restraint, and that as soon as you have consensual sex, you consent to birth any possible babies that might result. They affirm that the "tough cases" are exceptions though, because rape and incest are not voluntary and life-threatening pregnancies are largely unpredictable. And others say that abortion is wrong in every case because a baby's life is at stake. Whether it was conceived in rape or threatens the mother's life doesn't matter, it is still a human life and should not be murdered. This does not mean, however, that a mother whose life is threatened must die for her baby (especially since said baby, in most life-threatening pregnancies, doesn't survive), but that the procedures used to save her life should be for the purpose of saving her life, and not just for the purpose of killing her unborn child. This principle is called the "double rule".

As you can see, everyone has their reasons for believing what they believe, but until we can agree whether or not the fetus/unborn child is alive and human or not, the argument will remain.

Also, when it comes to the argument about whether or not same-sex marriage should be allowed, it is the definition of a few small words, and beliefs in different truths that cause the argument.

The biggest discrepancy I see with this argument is the definition of marriage. Marriage is a lot of different things. It's a civil union and often also a spiritual union, a union of love and commitment, but often also a commitment to raise children together. The difference is in the "oftens." Marriage is not always a spiritual union, and therefore the religious arguments against it are invalid in the name of religious freedom, so long as churches that do not believe homosexuality is right are not forced to perform same-sex unions. Marriage does not always foster love and commitment (people cheat on each other, and there are abusive relationships as well). And Marriage does not always result in children either, as many couples are deciding against having children, and therefore the argument that same-sex couples can't conceive children together is invalid, based on definition alone.
It is difficult to argue then, that adding an additional definition to the plethora of definitions marriage already has, will do society any more harm. Unless you argue for more absolutes in marriage than there already are: (i.e. that marriage should always be a civil and spiritual union, made in love and commitment, with the intention to raise children.) This does not mean that marriage will always be these things, but that it should always be these things, and the reason it is not, is because of human imperfection.
Another facet of this argument is the "right to marry." Supporters argue that everyone should have the right to marry, and that denying same-sex couples that right is like denying the African-Americans voting rights. Opponents argue that the "right to marry" already is extended to everyone (e.g. there is no one saying that those with same-sex attractions cannot get married, just that the other partner in their marriage must be of the opposite sex) and that the "right to marry whoever you want" is not a valid right because that destroys the purpose of marriage.
Supporters contend that the "right to marry" should be extended to all consenting adults so that they can express their love to each other. Opponents claim that marriage, as a societal institution, comes with the benefits and the desirability that it does because it is a society's stamp of approval on a relationship that is bound to bring forth the healthiest, happiest citizens. This is based on the idea that children raised by two biological, married parents are the most likely to lead healthy, successful, happy lives.
Supporters contend that it is two loving parents that make the difference, not necessarily the biological factor, and therefore same-sex couples should be allowed to adopt and raise children that are not their own, and have it be considered the same level of benefit to society as an opposite-sex couple raising children.
There is also the "love is love" argument; given by Supporters that homosexuality is an acceptable equivalent of heterosexuality so long as it is between two consenting adults. This argument states that because consenting relationships don't hurt anyone, they should not be outlawed. Marriage is society's affirmation of love between a couple, and those who favor the same sex should not be barred from it.
Opponents often differ on how to respond to this piece. Some opponents believe that any sex outside of a marriage between a man and a woman is morally wrong, and thus homosexuality is wrong by default, but so are any heterosexual relationships outside of marriage. Other opponents contend that homosexuality, as a behavior that only a small minority manifest, is akin to a mental disorder, or some other unpleasant, but natural condition, and that it should be treated, not accepted.
Supporters contend that there is nothing wrong with homosexuality, morally or mentally, that it is involuntary and therefore shouldn't be treated as wrong, and that pretending that there is something wrong with it is simply prejudice and irrational hatred talking. Opponents contend that, while same-sex attraction is not voluntary, that choosing to engage in same-sex behaviors is voluntary. They say that one does not have to have sex with every attractive person they see, and that sexual attraction is not rigid, but may change over time. They cite the many stories of same-sex-attracted people who chose not to act on their attractions because they believe it to be morally wrong as evidence of its possibility. Some same-sex-attracted people have even claimed to have changed their orientations from homosexual to heterosexual. Most simply rely on self-control.
Supporters argue that such denial of natural affection is harmful, delusional and naïve. Same-sex-attracted persons, in Supporter's eyes, should embrace their attractions and act on them, instead of remaining sexually-repressed, which might lead to mental and or emotional problems.

And the argument goes on… and on… and on…

But as you can see, neither side will come to an agreement, because they cannot decide universally what marriage is, or what it is supposed to be, nor can they decide whether or not homosexual behavior is involuntary or not. And since no one can universally accept whether or not there is a God, moral arguments about right and wrong under God's law cannot be accepted either.

*sigh* and so… the argument lives on.