He has the grounds to but the best we can do is mass-report that user's content. And also mention that user's ripping content from a game that Steam previously banned.
Take a look at the first sentence posted by this person.
"
As everyone knows, the game dev is very malicious to certain things (being defiant to CCP fascist), but I don't think this how we should treat him, therefore that's why we must pirate no matter what we can. "
Basically it's this:
"
Just because the developer hates our guts we shouldn't treat him like slime. This is why we must pirate his IP instead. This is fair."
Theft is never fair. Ironic that we're talking about this here, of all places
But most of us here love the game, political message or no. It's just that a good number of people have no means or particular want to financially support the developer.
I guess Steam wants a log in so we can't mass spam the report button with anon accounts.