Google+, or rather, Google-- at the moment

Someone has decided to share his Google+ posts with me. That's terribly kind of him. However, since I'm not in fact on Google+, this amounts to my having been put on someone's mailing list against my will—and I can't even reply to him, since all the mail comes from a "noreply" address at plus.google.com.

There's "unsubscribe" info at the bottom, but, seriously, I'm supposed to unsubscribe from a mailing list I never joined? What the hell? (In any other email, that would count as a spammer trying to verify my address.)

My feelings about Google+ have tilted from "slightly positive, because hey it's not Facebook" to "markedly negative, because seriously you guys are helping a user spam me?". Is there some sensible way to make this stop, perhaps by emailing some support address at Google to say "so when did you turn evil"?