Here's the flip side of that coin ...
Guys like Casey, as "hawt" as they may be, that act out like that, can be quite insecure individuals, seeking self 'validation' from others, through picking a 'victim' to publicly humiliate, in order to attempt to make themselves look 'bigger'/'better' than they, themselves, 'secretly' think they are. It's not only a shame, but also quite pitiful.
However, in order to 'reach' them, you first have to 'prove' that you can stand up to their deplorable (public) treatment of you.
That can be quite "tricky" though. Depending on the weakness of their own self esteem, turning the tables, humiliating Them in public, could possibly turn them into a real enemy that will only heighten their attempts to socially 'harm' you.
Then, again, standing up to them might earn their 'respect', and get them to back off, and, perhaps, even become a "real" Friend.
In that light, it may be best to walk away when others are around, but, when the two of you are alone, ask him if he really meant everything he said, and, maybe, even intuit that you might be willing to 'accommodate' his "guy on guy" curiosity, but only if he'd promise to keep it on the 'quiet' side.
Of course, if he agrees, and goes along, that still won't guarantee that he'll keep that promise, and not bring it up publicly in the future.
However, if that should happen, and he does "let the cat out of the bag", all you need to do, to drop him down a peg, or two, is to fess up to it, and ask why he seemed to enjoy it so much. It's THEN that you don't back down, or back off!
He'll LEARN! And, YOU will emerge as the Stronger of you two.
Either way, it's a difficult situation. Give him a 'private' chance, but also prepare yourself for a 'public' stand! (Should that become necessary.)
Since I don't actually know you guys, I can't predict what might happen in either scenario. And, the approach you may choose to take is entirely up to You!
However, in either case, do please let us know how things are going. And, I'm wishing You all the Very Best in this matter!
And, Yeah! ... As I've said before ... no matter what ...
Keep smilin'!!


Chaz
(It'll keep Everyone wondering what the Hell you're up to!

)