Or maybe it's because of people sometimes using "I'm just respecting women" to hide the fact that they're flirting with their crush. Or maybe some people are just immature and can't take a serious comment (e.g. "respect women") without making a joke (e.g. "SIMP!! lolol"). Or maybe they don't like being told braindead obvious things like "you should respect women", but don't know how to articulate that so they just resort to an idiotic insult. Maybe all 3.
Or, maybe they are sexist. Or all of the above.