Why are Lesbians afraid of penis?

I've heard that men are afraid of lesbians. See Answers.com question "Why are men attracted to lesbians?"

Maybe because they think that women need a penis to have fun, like men need a vagina to get off (most of the time). But actually women prefer a wide range of sensations, and maybe they are afraid of women's sexual power in that way. It's just a theory.