I tend to agree with Seinfeld about giving the finger. Why would another person feel bad when another person shows you one of their fingers ?
What do you think is the verbal equivalent of the finger? F*** you ! Or is it stonger, or weaker ?
I gave the finger to a guy just the other day. I am usually a pedestrian. I have no licence to drive. I had to cross the road. There is a pedestrian-only traffic light. So I pressed the button and waited ages for the light. Amazingly a break came in the traffic and I crossed before the crossing signal. When I was on the other side, finally the light changed for me and traffic had to stop for no-one actually crossing. A guy starts screaming his head of at me on the other side of the road. Finally I work out he is miffed that he had to stop even though I had already crossed. So, I gave him the finger. To me it is just my finger. But I know that to this asshole, he would get royally pissed off by me giving him the finger.
“Fuck you.” or “Up yours.” I’d be very surprised if there’s a third interpretation that’s not derivative of these two.
“Sit on it” would have been the slightly more politically correct version a few decades ago.
I’d say “Up Yours” is the more general Upward Thrust Hand with All Fingers Pointing Skyward.
The middle finger’s much more serious, so I’d definitely say an FU equivalent.
More serious? Maybe Double Middle Fingers, or MF combined with Other Hand Across Elbow Crook.
Oh no. It means FU to most anyone I know and I’ve seen people go seriously physical with someone for flipping them off.
FU, but being non-werbal, there is absolutely no comeback or one-up on this that I have ever heard pulled off well. Thats why people get pissed off.
obviously the derivative of “fuck you” and “up yours” has to be…
“Fuck Up” … 
In Spanish it’s “que te den po’l culo”, “someone fuck you up the ass”.
I once saw a construction worker give another one the finger and the second one replied “dude, I’m gay!¡ :p” “OK, so I hope nobody gives it to you up the ass then, damnit!”
I am not sure I understand you here, You are saying that a gay man would not be offended by anyone giving them the finger ? Is that what you are saying ?
I think the idea is that the gay guy (whether or not he was really gay) scored a direct hit with a comeback for a gesture that is typically difficult to give a good comeback to. So the guy giving the finger feels deflated at the rather non-angry response.
That, and it’s funny.