Lucien Favre's side had twice been pegged back at the Commerzbank Arena, and were forced to settle for a point after a late Thomas Delaney own goal.
Reus said: "This is really going on my nerves with your mentality bull****. Seriously.
"Today? Are you serious now? The 2-2 was scored due to mentality? Are you serious? We played dumb, sure, but don't come to me with your s*** about mentality. Every week it's the same c**p.'
"Our main problem is that we can't see out a game. But that has nothing to do with mentality. A goal like the 2-2 just mustn't happen. If we make it 3-1 this game is over but we also could have seen it out to win 2-1 but we didn't — that's it."