Blame for his death falls on Billy here. He was clearly warned that Tommy didn’t appreciate the reference to his past. Billy pretends to make peace and peace is accepted. Billy takes Tommy’s show of restraint as a symptom of weakness. He missed the mark and paid dearly.
I understand the need for humility. Tommy lacked the necessary humility in this difficult situation. I felt for his companions in this situation more so than him. They were there to enjoy themselves. But once Billy crossed the line, they were forced to make a stand. Ultimately, what got them there got them out. Tommy had to pay.