I never take my bag off when on the train, the thing is, if you put it on the floor then everyone kicks it and stands on it! I suppose it depends how big your pack is, I'm talking laptop bag size, I don't use backpacks like travellers.
I had a guy tell me to take it off one time as I rubbed against him once, he got all upset about it, I told him to go away. That was the end of that, I'm surprised it wasn't on Stomp to be honest! I had nowhere to put it on the floor. He kept trying to push me but he was too weak.
I suppose I am a douchebag too