Melez wrote:
Oh, lol. I thought it's a guy who puts a bot when going to the toilet.

Lol, you made my day
I think it comes from the "Coming out of the closet" generally referred to homosexuals who try to hide their homosexuality and eventually when they "come out of the closet" or; let people know of their sexuality.
In this case, it is referred to botters who pretend their legit by "hiding in the closet" and yea, you pretty much get where this is going.