How much can you trust your boss?

My boss and I after 4 years working together start to learn each other's style by now, to the point that I can lash out many things with him without too much worry about being accused or being betrayed. Today I may have crossed the line. I kinda told him that I think GM is doing sth unethical in the sense that he is trying every possible way to block another program (his political enemy) to move forward. My boss started stuttering. this gave me a hint that he was uncomfortable about the discussion. should remember to keep my mouth shut. get into trouble again.