Ignorant Is As Ignorant Does

No excuses for being rude, bad mannered, ignorant, self-obsessed, or selfish.

No excuses, and no-one else to blame.

Except being as thick as mince, and having the personality of a polystyrene cup.

They would be perfectly good excuses.

Never having learned, or observed, how decent people behave, and conduct themselves, how could you know any better?