Eclectic, I'd say internalised oppression is where you absorb all those societal messages that say you are of less value because of your ethnicity, class, sex, disability, immigration status, etc., and it forms how you see yourself. When women put themselves and other women down for things they wouldn't condemn if men did it, that's an example of internalised oppression, imho.
Beach, it's pretty clear from my posts that I was not "speaking for women of colour." Apologies to Sili, Eclectic or any other women of colour who might have felt I appeared to do so.
From what I recall on another thread, you don't identify as Lesbian (apologies if I got that wrong, however,), but if you saw a thread with content you thought might be hurtful to Lesbians, would you not speak out about it? From what I know of your political views, I would expect that you would, even if it wasn't from your own "self-interest." I would speak out, too.
One doesn't have to be directly affected by a form of oppression to call it out or condemn it. Likewise, if one isn't directly affected by a form of oppression, it's really easy not to even notice it. It's also easier to diminish it's significance, or even dismiss it when it doesn't affect you.
Applied to sexism, that means men can call out and condemn it. But, since they aren't directly affected by it, they may not even see it when it happens. Because it doesn't affect them, they can insist women are "making too big a deal" of it, or even insist it's rubbish and isn't even an issue.
It's the same mechanisms of oppression in different contexts.