I'm going to tell someone they're not a virgin
Why do you want to tell them they are not a virgin?
Because, I believe they need to know.
Even if you think they should know something, you would be rude to assume somebody is a virgin. You don't know and people will think you are a pervert.
I'm a virgin, so I can tell them. It's my place to tell them.
I doubt this person wants you talking about something that personal about them.