I would contest that if the industry wasn't demonized it wouldn't have a dark side.
EDIT: I would like to expand my previous comment though. Whenever prostitution is legalized we see massive improvements in the lives of sex workers. It seems clear to me that further reducing the demonization of sex, sex workers, etc would lead to a better work place in those industries for similar reasons. There may be a baseline of evil, for the reasons you point out. I don't think that should stop us from working to at least reach that baseline, rather than just leaving the people and businesses that inhabit that crucial landscape to rot.
What do we mean by "sexism" here? You don't think it's enough that men would like to have sex with attractive women? Or is that fact itself sexism?