it sucks a lot of emotional responses to distress are also emotional responses people associate with being dishonest. "ummm if you weren't lying why did you get so defensive" BECAUSE YOU ACCUSED ME OF LYING WHEN I DIDN'T..?
idk what you call this sort of "logic" but I blame the body language reader pop psychology people
also someone who has a VERY extreme reaction to being accused of lying most likely has had traumatic experiences involving these accusations so is much quicker to be defensive