You've obviously missed the whole point of the significance of the affair between Winston and Julia. It's not about the sex, or betrayal of Winston's long since gone wife, who at this point is a non-issue anyway. It's the fact that Winston and Julia find pleasure in sex and have therefore struck a silent (well, not really silent) blow to the Party, which has done everything in it's power to remove pleasure of any kind from the lives of its inhabitants. The goal of the Party is to keep its citizens entirely in a frenzy of hate and victory, for which there is no room for physical pleasure, or love. Therefore secual pleasure, as it says in the book (in these EXACT words) becomes a "political act."