Well personally whilst I dont blame Nani in the slightest, I also don't blame Gomez either. The handball was so blatant that I think everyone else on the pitch just naturally assumed that a free kick was warranted.
The linesman was looking directly at Nani and you could see from the replay that he saw clearly that Nani handled the ball.
As mentioned by Redknapp, even United players were assuming that a free kick had been given. Nani himself even looked over to try and figure out what was going on, so he himself wasnt sure. Neither did Gomez appear to know what was going on.
The linesman didnt flag at any point until after the spurs players had surrounded him. He then stuck his flag up. Whether the spurs players had said something that he felt justified the refs attention, or whether he then realised that he ( like everyone else ) was wrong in the assumption that the free kick had been given, so he decided to consult the ref and explain what was going on.
The decision on paper, was 100% correct. The ref hadnt blown, and if he's not seen the handball then he is 100% right to allow the goal. However the linesman clearly made a monumental feck up by just assuming the ref had awarded what clearly was a blatant free kick. His only justification could be that it was so obvious everyone barring Nani and Clattenberg just assumed it was a free kick.
The spurs players have a right to be aggrieved. It was a shocking piece of poor decision making, not by the referee but by the linesman who has to stand and hold his hand up and admit he didnt do his job properly.
Once that ball hitt he net Clattenberg could not reverse the decision and I think that is what he explained the the linesman. he could not retrospectively give a free kick to spurs because he hadnt himself seen it, and had thet linesman done his job properly then the ref could have changed the decision and he would in fact have been 100% right to.
Terrible goal, and doesnt do the game any justice, but that said, if the linesmen dont do their job properly then thats what is going to happen.