Is informing your advisor about a community cause considered unprofessional?
I don’t think that there is a norm for this kind of interaction, and I think that’s a good thing. Some people will be interested in talking about it with you, others will not. It wildly depends on who your advisor is and what they care about.

It sounds like the issues you’re talking about are issues that are in vogue in the US, a country you aren’t from and potentially have never visited. I would leverage that as a way to talk about it with your professor. Ask the professor about it casually. Say that you have been reading a newspaper or blog or something, that you heard about this political issue in America, and that you were interested in getting his perspective on it. Presumably you don’t know a lot of Americans, and it’s natural to ask one who you already have an established relationship with about it.

Bringing it up in casual conversation is a lot better than email, in my mind. There’s less of a chance for the message to get lost, and I know plenty of academics for whom that’s a major factor.