I'm a United fan and I thought it was a soft penalty. But your simple logic does put it into perspective, I also always ask myself, would it have been a freekick outside of the area? And in this case I'm sure it would have, so there should be no arguments?!
Also there was an incident just before Giggs was taken down in the area when Johnny Evans was pushed from behind in the area and that wasn't given. This also was more of a penalty but we never here about these decisions from the blind anti-Man Utd Liverpool fans!
On a side note Gerrard's tackle was nasty and deserved a red, having played football at semi-professional level myself if that would have happened to me or one of my team, I would be very unhappy.