Looks like we definitely disagree! When you say cursing is something that affects others, I don't know how you can ignore those that see you flipping the bird and not say that's the same thing.
Again, when you fly the bird you are cursing out that individual, saying "f you". If Hak says "f that" or "that's fing baloney" no one cares. But if he yells "f you Adam!" it's the same thing, except only Adam and the players here him (unless he's on tv). But when he flies the bird the whole arena can see it.
So yes, to me, there's quite a difference.