If it was just the message, maybe you could argue that he overreacted. But it isn't just the message, he can also no longer use his profile.

And why is that? Probably because some algorithm thought his profile impersonates someone else, which is apparently not the case.

And the way Google choose to communicate their suspicion and the actions that followed it to their user was by (practically) saying:

"You did bad thing x, and now you have to pay the consequences for it."

Can you see his point better now? (Personally I can fully understand him)

EDIT: Oh, and a better approach is mentioned in this HN-comment: https://news.ycombinator.com/item?id=6732820