why does Tom attack Myrtle at the end of the party?

The group becomes exceedingly drunk; as a result, Myrtle begins to grow garrulous and harsh. Shortly after Tom gives her a puppy as a gift, Myrtle begins chanting Daisy's name to irritate Tom. Tom tells her that she has no right to say Daisy's name; she continues taunting him, and he responds by breaking Myrtle's nose.