I think it's all about perception. Depending on what threads one is looking at, one person might encounter more where the consensus is against the OP, and another where everyone defends the OP. I think this is also one reason we avoid politics here for the most part--it's hard not to see things through that lens.
I notice sometimes one person will complain about being 'jumped all over or 'dogpiled' when it's really just a lot of people disagreeing, and sometimes even a few folk disagreeing. So the line isn't always clear. I can think of a couple of threads where pretty much everyone felt a particular way, but most of the posters were polite. It just can seem overwhelming.
Sometimes there'll be a thread that's pretty well split 50/50, or even 30/70 in favour of the OP, but the OP will come in and say "I really regret even posting this thread, you can all go back to bashing me now, I won't be coming back" or something similar, leaving people going 'Huh'.
Also these things tend to snowball so you might get a thread where someone complains about a tasteless joke the friend made, and on page 1 people are saying 'definitely speak up if you're upset, but this doesn't seem like that big a deal' and by page 4 it's 'I would *never* be friends with someone who made that type of joke, I would immediately kick them out of my house!'