The default policy is already not to relay invalid data. But it doesn't help under adversarial circumstances. It doesn't help if there's miner collision, and you are getting invalid data from them and have no means to know it's invalid. It doesn't help if they are relaying invalid data to you on purpose.
miner collisions are just 2 miners that solved at nearly the same time.. the data isnt invalid, they just solved relatively at the same time. each of these miners wont invalidate their block. its for the other full nodes to check both blocks and when both are valid. then check who solved first. and the not relay the loser..
there is no point marking the loser as invalid and still relaying it.
there is no point in a miner marking their block as invalid. as at the time of solving and relaying to that very first peer, they dont know they lost.
thats for the network to decide
Of course it's collusion, not collision. I made a typo.