checking partners

[chimpanzepoopdic]

The game I play in is a extremely loose and crazy 10/20 limit game. There are 2-3 guys playing every night that if they get heads up together they will just check it down. It doesn't matter if they have a hand or not. I havent said anything because they dont seem to be whipsawing or trying to push others out of the hand when they are in the pot together. But if they happen to get head up they always check it down. Is this ethical in your view?