Personally I don't think it is ok. But I don't think it happens much at all, not our fans. I spose the word "wanker" is used but I'd take that as generic bad language rather than a massively sexual insult.
But yeah, I agree it's both ways.
Although I still think there is a slight nuance...
I think, no matter what incitement a player gets from the crowd, anything involving swearing or sexual gestures are where the line needs to be drawn - at the end of the day a player is doing it to everyone (kids etc), not just those that 'deserve' it.
But making "2-0" gestures? What a joke!