I don't want to date a girl because I don't find her attractive but I'm going to do friends with benefits.
Don't you think that might hurt her if she found out?
I don't think so.
I understand you don't find her attractive so you don't want to date her and just want to have sex with her. By doing so you're giving false hopes to that girl. You should not mislead her about the relationship status.
Oh well, I'm dirty and I enjoyed it.
That is wrong. She needs to know the truth, you can find someone else willing to be FWB .