It was not a small thing. If the information that Excalibur had was actually exposed out to the public and even worse, if the information reached the mafia world, then all the assassins would have been killed at some or the other point of time.
They and Italian mafia are always at loggerheads as they got many missions to kill some men in Italian mafia who were in high positions. So, they were one of the groups, they always had to be careful about.
Chance could imagine the stress his father might have gone through. He kept kicking and punching Excalibur while all these thoughts were going on in his mind.
Excalibur was already weak and not physically trained as for the last few years he was not in the field and didn't maintain himself well.
Chance was already aware of it, as he himself observed in Miami. Taking advantage of it, Chance beat him up even harsher than he intended to.