Actually, I don't think NASA really wanted to launch either. It was our fearless leader, Ronald Reagan, who really wanted to launch then because he felt that another delay would "look bad". I remember seeing on 60 Minutes a NASA engineer who, the night before the launch, had spoken to President Reagan about the effect of the cold on the O-rings (which are precisely what failed). Reagan, of course, insisted that the launch go ahead.
Ultimately, it was our own arrogance and Reagan's ego that caused the explosion of the Challenger and the death of its seven crew members.