Cash Game Check it Down or Chop

[ed08724]

I was recently playing in a 1/2NL home cash game. We try to play by typical casino rules. The following situation came up. There was a raise before the flop with 3 callers of which I was one. The flop was all one suit. I hit top two pair on the flop and made a $25 bet. I got called then raised and I folded. The other caller called the raise. The turn went with both players checking. On the river the caller asked the other player if he wanted to check it down and the raiser agreed. The raiser then proceeded to turn over the stone cold nuts. I asked why he would agree to check down the nuts and he said he just wanted to be friendly. The pot was a little over $100 at the time. None of these players have ever asked me to check a pot down. One of the other players stated that once it was heads up they could do anything they wanted including splitting the pot if they wanted.
I was upset and cashed out and left. It seemed to me if they were going to play hard against me and soft against certain other players that is kind of cheating. I would not have won this pot anyway but it could have been possible.
What is the correct rules? Can you verbally agree to check down a pot after someone else was bet out of the pot? Can you agree to chop a pot after someone else is bet out of the pot? Thanks!