Your 15 year old son has a best friend.
They have been best friends since they were around 7 years old.
They're playing video games and you pass in front of the door to the room they're in and overhear them "johning" in the midst of a heated battle.
Son: That's why you like boys.
Best Friend: That's why the only girl you like likes me.
And they keep at it all in good fun.
Later you tell your son it's not nice to pick on people using gay slurs in any way to insult someone because you're a peace and love kinda mother.
Your son is confused and you tell him that you overheard him teasing his best friend about liking boys.
Son: But he does like boys.
You're shocked...because you didn't know this and play it cool by asking...
You: How do YOU feel about him liking boys?
Son: (shrugs) I don't feel any kinda way...I like girls. I don't care who he likes like that.
And your son keeps it moving like it's no big deal.