Because they are? I mean, it's either they're bigots or they're idiots, because Abby's body proportions are completely reasonable and you'd have to be either an idiot or a bigot to think otherwise. Either way, I don't respect them and they don't deserve respect.
Its just using those words in cases like this kinda lessen the impact of them. People become more suspicious when real bigotry and sexism occur. Same with words like racist and homophobe. Save your anger for the people who really hurt others.