It's true, but it was all totally done in jest. Costas made fun of Marino's jacket, and Marino smacked him on the back of the head, like "whatsamatta witchew?" It was just horsing around. No need to go Merc on it and suggest that no TV anchors should speak without attorneys present.
Yes, it DID happen.
Yes, it was done in jest, but Marino was visibly po'ed at Costas. Marino is not one to be able to disguise his emotions very well, as we know, and you can tell by his body language and his demeanor that he would have preferred to give Costas a mouthful of fist instead of a semi-playful slap.
It is not something that is going to be "covered" as a news item, it was just an interesting exchange between these two on a show that is taped in an unrehearsed fashion.
I thought it would make for an interesting post as I'm sure many of us would like to pop Costa's (on air or otherwise) from time to time.