Either way, I despise cellular phones in general, and headsets don't help. Either way, people are blabbing into thin air and ignoring the people near them. Disgusting state of being for society to me.
I think it's perfectly within Wally's character to press the limits of what he can get away with. Besides, though he is frequently an apathetic individual, this would not be the first time he has expressed a tooth-grinding frustration directed towards the boss.
It seems... contradictory of Wally, who normally cares so LITTLE about anything, to yell so vehemently at his boss... It seems a little out of character for him.