Absolutely. My kid's school has been having affinity groups this spring (broadly, racially-based), and guess what - there's a white kids group, and that's fine. They don't talk about how the whites are oppressed, but how they can be better allies and understand the hurdles other groups face. Or, I have a friend of a friend whom I friended on FB specifically because he is a cis white male and kept making comments in friend's posts that were really thoughtful and insightful, and I said to myself, self, I need to see more people like this in my life, and it turns out he would host a monthly men's discussion night where the gathered men would discuss being allies, understand their privilege, understand viewpoints from outside the cisgender male perspective.

THESE ARE GOOD THINGS. This short letter is scanty on the details, but it really doesn't sound like that's what this is. In particular, if it's setting off alarm bells in other ERGs or affinity groups, that's something to pay attention to - usually minority affinity groups are like, hell yes, go and talk amongst yourselves and educate yourselves and figure this shit out so we don't have to do your 101 level work for you! If that's not their response now, that's telling.