Be careful with how you choose your words. Is it a disclaimer to ward off confusion or a badge of honor in order to state their political/social stance? There's a difference. They make the disclaimer or badge clear because its a portion of their beliefs that they feel strongly about and should be taken as the same type of symbology as an inverted cross. If you know anything about the radical left and people who truly adhere to opposing racism and other types of prejudice, the amount of passion and vigor is about as militant as any extreme belief system; far from any kind of "let's all be nice" mentality. In fact, I'd argue that people who are amongst action groups - philanthropic, dissident, militant, extreme, moderate, whatever - are more active and at work than these boyish men dressed up like vikings. It's not a matter of being a bitch or selling out.
And on the matter of selling out, being anti-racist and anti-homophobic is too mainstream. Last time I checked, minorities such as gays are oppressed by the same forces (religion, conservatism) that black metal bands aim to mock and remove from power. Those labels that are clear with their support of minorities and refuse to carry NC releases are actually a hell of a lot more important than the stagnant and socialnorm preserving black metal bands that support racist/prejudice. The idea of any truly radical idea and, by extension, band/musician is to crack into the mainstream. What is much worse than "conforming" into some kind of mainstream monstrosity that you seem to be afraid of is how bands and fans have an obsession for black metal artists to fit the mold musically, ideologically, and image-wise. Whatever Mayhem was doing at their time, cool. However, it's fucking 2011 and whatever ideological grounds the genre was built up on and tradition need not be followed in perfect line. Euronymous and Dead's time that you speak of is irrelevant and the need some people have to resurrect it within the current age is a preverse form of retromania.