Cyclists, do you cycle on pavements and/or footpaths even though it is illegal?

Earlier this evening I was walking along a footpath by the river Thames with my girlfriend. There was another couple walking a few yards behind us who were not with us, and as we all neared the end of the path a cyclist came riding toward us. When he saw that none of us was about to move to let him p, he became sarcastic and my girlfriend pointed out that he was on a footpath, and should not be cycling there. He became abusive so he and I then exchanged words my last ones to him being extremely rude. If you cycle on pavements and /or footpaths, how do you react to somebody chastising you?