I'm on other forums, Disney related and not, and I have to say that the DIS is the least bad. On those other forums, people straight up insult each other and call each other slurs. They have "no politics and religion" rules too but they're ignored every day. Facebook, Twitter and Reddit are WAY worse too. Some people just really like being argumentative and to debate with others. That's why on every social media site out there (here included), the threads about negative topics get WAY more attention than positive ones.
I do find it funny that even the most innocent of threads can get "derailed" and it turns into a big debate. My favorite ones are ones about parenting and weddings. Those rile up the most people. The one about someone not dressing up for a wedding got people heated. I can't wait for the meltdown that'll happen on a thread about a dry wedding or a childfree wedding.
In terms of people being snarky and/or passive aggressive, I just roll my eyes and scroll down especially if it's coming from people who constantly do it. Sometimes I've done it during discussions that I'm passionate about and I'll admit that. I do notice that it happens the most often about the most useless topics LOL I was surprised to see it even happen on that one thread about picking up your kids from school.