Disclaimer: As a theorist...I am an epistemologist first (an educator first and a half), an ethicist second , and a politics guy 3rd.
The problem of human response to threatening evil is a complex one, but the set of responses seems to be roughly two:
1. Become evil yourself, so as to combat the evil.
2. Oppose the evil without becoming evil.
2 is much much harder to do. Ghandi is revered rightly for responding to evil with non-evil. MLK is rightly revered by many while Malcolm X is revered only by few because MLK responded to evil with non-evil. The open source software people, rightly incensed by closed-source software and especially software patents, have responded properly, without patent thickets.
In some cases, 1 seems to be the only choice. When attacked in the War of Independence...the colonials had no choice but to shoot innocent men who had loyalty to the wrong person(George). In World War II, if people had known about the Gas Chambers, we would have had a question of a Moral duty to respond with evil. All our other wars of conquest are substantially less defensible.
Racism is evil.
Some folks suggest that we be counter-racist...become evil ourselves.
I hold that becoming evil is the wrong choice. Oppose the evil of anti-white racism. Oppose the evil of pro-white racism. And call an evil spade an evil spade.