Crusties are very proud of their state of filth. A step on you'll find the unwashable. Unwashables truely and deeply loath any form of personal hygiene. An unwashable is a religiously hardcore mysophile who usually stays unwashed & crusty all his life. For them it is not so much a temporary statement of believes as a dedicated way to live, despite often being shunned by society.
He's so incredibly filthy, he's even worse than those crusties, he must be an unwashable.