It's because he was drunk. The old man had too much wine.
At dinner Frankie tells this to Michael, in Italian :
"Hey, Michael - excuse me. With all respect I didn't come here to eat dinner!"
And then knocks over the glass.
Then he later goes on to tell Michael, in Italian :
"You'll have to excuse me -- I'm tired, and I'm a little drunk!"
So like Michael said, "That old man had too much wine."
Don Cardi
