Why would someone purposely out someone ? I suspect I may have been outed to my crush but in a very derogatory way
I think some people think of it as an ice breaker. "this is my friend so-and-so. He's gay." just in case the person they are introducing you to finds you attractive, or is curious about whether you are in a relationship or not. Because, apparently our sexuality is an elephant in the room and we can't address the issue ourselves without someone doing it for us. That's how it feels when people do it to me, any way.
I would suggest that if you don't want to be completely out then be careful who you tell, and when you do tell them, make sure to say that you don't want them to tell others without your permission.