A while back, probably over a year ago, I made a comment on Reddit expressing my distaste for dogs in a fairly provocative manner. It shouldn't have come as any surprise that this trolling was met with some amount of hostility, most notably, the 'ol "AS IF cats are any better!"
It was just assumed that because I disliked dogs, I must like cats -- that pet preferences can be summed up in "either dog or cat." Of course, it's possible to dislike or like both animals, but because some people understand the preference as being an either/or scenario, my comment was likely to provoke a response in which the justification for the preference was framed in a false dichotomy. To serve as another example, "Democrats suck" is likely to produce several responses about how terrible Republicans are.