Now, I'm not saying Grant lived by these rules himself on Survivor, but in his mind, as a pro athlete (and as a pro athlete who valued integrity toward the game and his teammates over winning by using duplicitous means) Rob's actions toward Grant are essentially unforgivable in Grants mind. What's worse, Rob doesn't get this at all- he doesn't understand honor and integrity in playing a game-it's not even on his radar. You don't betray your teammates trust, you don't purposely make them look stupid and you certainly don't so it with a smug smile on your face.
I'm not saying Grant is some sort of saint but I do believe there is a code of honor some athletes do live by and Rob just doesn't comprehend that.
Anyhow, Rob did say he wasn't there to make friends, so why is he so obsessed with Grant not wanting to be his friend? Move on, Rob. Not everyone has to like you.