"The thing is, rapists absolutely need one thing to operate. They need people to believe they are not rapists. Stranger rapists do that by trying to hide that they are the person who committed the rape. Acquaintance rapists do that by picking targets who won’t say anything about what happened, or by using tactics that, if the survivor does speak up, people will decide don’t really count as rape. If you want to do something about rapists, make sure people know they are rapists."
This article contains some very useful, very concrete tips on how to attack rape culture in your social circles