However, some protesters say they support the troops because they don't want them to be killed. How does one answer that? Of course, some of these people will not accept any counter-argument. However, I would say that we have been fighting a two-week war, we've taken less than 100 casualties and nearly "conquered" a country the size of California. This is a great, largely bloodless operation. And "peace" demonstrators who express unhappiness about it are showing their hand: they DON'T care about the troops. They DON'T want the mission to succeed. They're unhappy because it's going well.
I would also add that military might exists for a reason. We have a volunteer force. Everyone in the military today is there with the express understanding that they may be put it harm's way. That's their choice. To say that "I support the troops, and I don't want them killed" is to say that I support your desire to be a policeman but I hope you never catch a criminal or help reduce the crime rate.
"Gee whiz, thanks fer yer support!"