"Issue purity" (as I'm using it, anyway) is the way activists boil down the issues of an oppressed group of people to represent the interests if privileged people among those oppressed groups, considering anything that doesn't represent those privileged people as a "side issue" or a different target. I thought about this today when, after somebody critiqued the premise of the book "Lean In" for not representing low-income women, somebody responded:
Here's an explanation of the difference here.
Your essential target appears to be class, and you don't appear to be testing for logical causality. For many other feminists, the essential target is gender - so that the important task (under that kind of thinking) is to address inequities targeted at people exactly and causally because of their gender, as opposed to addressing all "injustices" that happen to hit a lot of people that happen to have a gender.
And you know what? They're wrong.
The reason they're wrong is because you can't boil down women's issues--or any social issues, for that matter--into a convenient set of issues that are purely related to that one group of people only. Trying to do this nearly always results in privileged people being the focus. The women who wind up being the "pure" representatives are white, relatively wealthy, heterosexual, and otherwise privileged women; issues relevant to low-income women are class issues, not women's issues; issues relevant to black women are race issues, not women's issues. This is the case even when said issue is pretty much unique to women. One of the most prominent examples is the assumption that trans women's issues are more trans issues than women's issues, even when those issues rarely apply to trans men (or only apply to us when we're still viewed as women).
But it's not just women's issues that has this problem. It's every major social justice movement. The LGBT movement, for instance, tends to boil down its issues based on the needs of relatively wealthy white cis people--often men--while ignoring issues relevant to low-income LGBT people, LGBT people of color, trans people, immigrant LGBT people, LBT women, transnational LGBT people, and so on. The fact that the first thing people think of with this movement is "marriage" rather than something like "employment non-discrimination" or "the right not to be murdered" is just one way this rears its ugly head. Just like feminists often would rather women of color's issues be handled by racial justice movements, the LGBT movement would rather not have to deal with issues specific to LGBT people of color or low-income LGBT people. Actually doing this, after all, would necessarily result in privileged LGBT people having to own up to their own oppressive behaviors, and we can't be having that.
What we ignore in all these cases is that intersectionality includes privilege. Every one of these so-called "boiled down" issues of sexism, racism, homophobia, and others exists on the intersection between sex, race, or sexuality with privilege. An "essential feminist" issue is not an essential feminist issue, it exists at the intersection of "woman" and "cisgender," "white," "straight," and "wealthy." And so goes it for most other social issues.
You just can't extract them, but unfortunately it appears to me people won't stop trying.