Pushing can be pretty useful in DR, I do not want it removed. Sure it is irritating to get pushed off an edge since you are taunting or using a misc item like bonk or a sandvich, but oh well. DR is competitive, every player wants to win. If that means I push you off a ledge because you were being dumb and taunting constantly, oh well your fault. Pushing is also useful for those pesky players who run out of spawn then go AFK, so you can just push them off the map and continue the round so you don't have to wait for them.
Griefing is a pain, yeah I can see the argument to have collisions removed since it is irritatingly hard trying to platform on tricky areas with someone purposefully trying to push you off, but that's why I have the high 5 taunt, they try pushing and I wait in the taunt until they move, griefing should be frowned upon, even IF this is a competitive game mode.