I think I've said something like this before: It's not so much that there are differing opinions on a topic, and that you will probably never get a compromise between Side A and Side B - but it's HOW the opinions are stated that really get folks riled up. If you assign a value judgment about people who do "x" (EX: "*I* would never be caught dead eating purple noodles, as it's so stupid and anyone who eats purple noodles is an idiot/uncouth individual/lazy/has halitosis"), then yes, a fight will break out between the two sides.
I have read some of those heated threads, and I've seen people making comments like "Well, if you do X, you must not care about your pet/child/husband." I mean, WOW, what an assumption to make!