Because playing nasty has been very unhelpful to the other side ? Because it helps to have an image of benevolence, “niceness”, and Christian charity ?
McCain has every reason to be a gentleman, including engaging in polite hypocrisies. That takes focus and discipline. He is not there to indulge himself or please us, he is there to win an election. Every word has to be calculated.
It would be very satisfying to a lot of us partisans to hear a thorough rant against our enemies, but that wouldn’t help in the big picture.
It also helps to remember the following fact. Twelve hours after the last time McCain "made nice" to Obama, he literally turned Obama's world inside-out, the effects of which have still not been fully calculated. Think about it...
the infowarrior