A strong imagination does it for me. I used to love eating lamb, but in my teens my father took me to a friends house where I partook in slaughtering a lamb and later eating it. Now I find eating lamb utterly disgusting. If I even smell lamb it reminds me of how the animal wailed around as it was dying and the smell of its intestines and skin as we butchered it.

Same idea with insects - when I picture someone eating insects, I get reminded of the smells, the sounds, and worst of all where they've been. Bees?! Ever seen a portable toilet in the summer when the doors are left cracked open and insects get into? Bees on human feces. No thanks.