Asymmetry of Purity and Contamination

 Virtue does not need vice. Vice does need virtue. 

 I can't say why, but I'm forcibly reminded that vice regularly pretends that virtue needs it, in an attempt to present the situation as symmetrical. 

 Vice is weakness. Without a virtue-fuelled rocket booster, it can't go anywhere or do anything. Vice has no power on its own, but it can borrow the power of virtue.

 Glory has no practical limit. A little glory is a little great. The more glory, the better it is. The rich get richer; the more glorious you are, the easier is it to create more glory.

 Vice has a limit. At or beyond 100%, you die. You are annihilated. 

 This is why a small amount of glory does not contaminate or undermine vice, but a small profanity can contaminate almost unlimited amounts of virtue. 

 A small amount of virtue in a sea of vice feeds the starving abomination.
 A small of vice in a sea of virtue turns the virtue into a giant booster for the vice. 

 That said, there is a solution. Perfect purity is unnecessary, which is good, as perfection is contrary to existence. Vice is weak, so weak that merely deciding to oppose it can be enough. Intending to become less vicious is sufficient. Security, as always, is affordable.

 To avoid writing a whole doctorate thesis here, let's say vice is okay if it's decreasing. If it is not taken for virtue, it cannot cooperate with virtue, and can't devour the glory in its environs.