Despite them being different bosses, I think it's kind of stupid to say that Chin wasn't afraid of Gotti. I mean, we're talking about killers here, both of them, who were in charge of big families. There had to be at least some thoughts in Chin's head(after the failed bombing and whatnot) that Gotti might try to seek revenge. But I'd say that's pretty normal for the lifestyle they lived, you never knew who'd go after you and why. I mean, shit, Gotti did take out his own boss.