It's an interesting idea to follow.

So a buisiness that isn't any of the many that might legitimately have pictures of naked women in their offices or other public spaces where employees have to work, has them.

What makes them a hostile work environment? Hostile or harmful to who, and by what mechanism?

I'll proceed on the assumption that it causes women to feel threatened by the men in the area and/or the owners/managers who installed the posters.

This line of reasoning is essentially the same as blaming women for the rapes they endure because they should have made sure they didn't look attractive to any men, instead of holding men to a standard to be responsible for their actions.