1) I don't necessarily think using a racial slur (ESPECIALLY how Incognito used it, but even otherwise) automatically = racist. But that's just me, everyone is obviously entitled to their own opinion.
2) That's the thing, his JOB was about to be taken from him. He has other mental issues and was probably going to be put on the NFI list and not paid his salary for the rest of the season once the meltdown happened. Rather than call it what it was, which is a mentally soft player coming to the realization that he can't handle the NFL (again, nothing wrong with that, the NFL isn't for everybody) game and that it was taking an enormous mental toll on his psyche, he used the team and Incognito as a scapegoat. And what do you know, just yesterday, the Dolphins decided to not put Martin on the NFI list because of the ongoing investigation, so he'll continue to get paid.