With the defeat, Leopards remain just one point above the relegation zone and it doesn't get any easier with a home tie against Kaizer Chiefs to come on Saturday.
Kerr slammed his players for not having the right attitude during and after the game and said they committed suicide by gifting the ball back to Pirates regularly.
"We were lucky to escape with just two goals," Kerr told Supersport TV.
"We gave them the ball too often and should have been punished. It was suicide. On another day, it could have been easily three or four. Micho should be a bit angry with his strikers because they had plenty of opportunities, but the opportunities came from our poor decision-making.
"I'm absolutely gobsmacked. I was out on the pitch at the end of the game and my players were laughing, making jokes and we've just been beaten 2-0.
"Their chances have come from our mistakes and we're better than that. Tonight in the second half, we were killing ourselves. We kept giving the ball away and that's not how we play.
"I'm angry. I've been nice to these guys. I can't get in to them too much because we've got a big game in Thohoyandou on Saturday against Kaizer Chiefs. I'm looking at the body language in the last 20 minutes and even the experienced players' heads were down. I'm not happy, not happy today. My team is better than that."