And why such a strong link? I think it's because the two words are almost synonymous. Sure, not all rabid ones are feminists, but pretty much every feminist is rabid. (Humour, on the other hand, is rare in them. It's why so much right-on "comedy" makes you wanna barf, not laugh.)
Given this association, it's not surprising that the Oxford Dictionary uses "rabid feminist" as an example to illustrate the adjective's meaning. Hilariously, feminists unwittingly confirmed its validity with their, er, rabidity -- something the dictionary's official Twitter feed elegantly pointed out:
If you click on the tweet they're citing you'll see that the feminist in this case was male, not female -- which might have been one of the reasons that they decided to skewer him. Dread to think what the reaction would have been like if the offended tweep had been a sob sister instead.If only there were a word to describe how strongly you felt about feminism… https://t.co/mAsmjUBoOs— Oxford Dictionaries (@OxfordWords) January 22, 2016
She prolly woulda labelled it harassment, and called in the plods! I can just imagine the scene outside the publishing house: "Let's get some muscle over here. Throw the book at the book!" Given how ludicrously thin-skinned, petty and punitive today's feminist chicks are, this is certainly not beyond the bounds of possibility.