Purse was booked in the second half of the Newcastle clash for throwing the ball down after referee Steve Bennett had awarded a free-kick against the Blues defender.
That moment of petulence left Bruce furious because it is in defence that the Blues boss is already without several players through injury.
"The booking for Darren Purse was just ridiculous, he deserved a yellow card," said Bruce.
"It was downright stupidity. If you throw the ball away, we all know you get a yellow card and he knew he would be suspended. That'll cost us dear because the one thing we are short of at the moment is defenders.
"Some of the other decisions and bookings I'm not going to bother commenting on otherwise I'll get myself in trouble.
Some of the decisions baffled me to be brutally honest. But I'm not going to bleat because we were beaten 2-0 fairly and squarely."
Newcastle: Match Photos CLICK HERE