Sometimes you have to fight your own battles
So if he bumped into me accidently with no apology because he's a caifone,I'd just let it go
If I knew for sure it was deliberate because there was no spaces and he thinks he's so important that he could just push people around to get by with no "Excuse me" I might say "Oh Excuse me,Its the king. And wave him by me and say Go ahead King"
If he bumped into me deliberately just to start trouble,I'd say nothing and wait for his next move.
But I don't think mentioning the Gambinos or anybody ellse would be a factor in however I'd react
In other words,if it came down to a fight,and I was able to beat him up,I wouldn't lose sleep worrying about the Gambinos going to avenge him for some stupid fight that he went out of his way to start. Maybe I shouldn't these days,but I'd think the guys at the top are still smart enough to not want to get involved in things like that..If I started the whole thing and he got beaten,then if I believed he was a Gambino,I'd worrry.