Let me ask you something.
Back, say, 200 years ago black people were slaves, being homosexual or non-hetero was criminalized and women couldn't vote, rape within marriage was also basically legal. Now, if you live in this time period, would you live in peace? Would you say "Why should people fight?" and just try to live in peace and work with everyone and let these things stay without any objection? Cause if you wouldn't, then that's the reason people fight.
My concept is, when people say "Why can't we live in peace and harmony and respect each others opinions!", people fail to realize that in itself, that's an opinion and a view. You're asking people to accept your view of reality, you're asking people to accept everyone, not everyone wants to accept everyone else. To me, when people say this, it's less "Believe what you want" and more "Believe what I want you too", which is to accept everyone regardless of race, religion and what-not. Not saying that's an opinion I disagree with, I do agree to accept everyone, but I'm just pointing out that not everyone has the same view. You might ask "Why do people not accept everyone?" and that's a whole different conversation as a whole. But even the "accept" everyone shtick can cause conflict, which I won't go into, but there are people you'll hear, with very strange stories and opinions that you may not be so willing to accept.