I’m inclined to agree with your thoughts. However, you are taking away your power by saying “please don’t fuck me”. It suggests that you, as a friend, are willing to engage in sexual intercourse and assume that the nature of your relationship will change from friends to “something more” as a result. It seems that you have learned (as have I) that not everyone thinks the way we do. Some are even devoid of morals, which it sounds like you have. Keep your power and say “no” up front. Put on the brakes and discuss how this might affect your friendship. If the guy walks, he wasn’t really your friend to begin with. You have the power to say “no”.