Yes, let both mullahs and their opposition know that this time around the opposition really have something to fall back on, even if mullahs try to kill all of them. Mullahs would have a real tough time to crack down on protesters, if American troops are on stand-by next door in Iraq and in possession of all those surplus arms from Saddam's regime.
The situation is completely different from Tienanmen Sqaure uprising. The brutal quelling of protest won't be the end of the story. On the contrary, it will make things much worse for mullahs. That is, Bush could come in and clean their clock, one way or the other.