You can't get consensus all the time. So what you're left with is simple respect for the individual. Different opinions are a good thing, it's part of how we learn. If we all thought alike, we'd be a very different place. But right-fighting is useless, because it rarely achieves anything. There is also a difference between discussing something, sharing views, and "winning" an argument. I think the board is about the former. We exchange views, but ultimately, given any topic, ought to be old enough to be able to accept that our own opinion is just that, and others can have valid reasons to feel differently.
Still, some topics are obviously more touchy than others: Healthcare, Guns, politics, religion, and apparently now, abortion. This is my list of "never discuss with an American" topics.