Why is everyone giving Acerblock such a hard time?
It should be pretty obvious to everyone anywhere that it is not socially acceptable to say things like that to strangers.
Particularly children.
OP may be 13, but that is still well under-age. The concept behind the joke itself is disgusting and vulgar, and most certainly should not be directed at a minor.
If some stranger in a public toilets were to make a loveual-joke, which could easily be seen as loveual harrasment, to your young teenage child, you'd be absolutely fuming.
And if this person has no grip on social norms, then there is something fundamentally dangerous about him. That sort of comment can easily get someone arrested or worse.