I've seen on here a few times people raise the question of whether or not to let their trainer know they are gay. Since this is my soapbox, here's my two cents.

Why? Why does that need to be discussed?

"Well they need to know...."
No they don't. What in the world makes you think they "need" or even want to know that?

If you seriously think your trainer needs to know what you like to do with your private parts then you misunderstand ...