How did michael come to such a conclusion. I know that Vito says that whoever comes with barzini meeting is a traitor. Even at Vito's funeral, michael tells Tom about this. But how could he be so sure? Why couldn't it have been a genuine meeting to make peace. Why didn't Tessio pretend as if he did not understatnd why michael refused to go with him in the car? Is it described in the novel (I haven't read it yet)?