Exactly. It looks like. You can't just blame authorities because they arrested him for investigation while the only thing you know is that it looks like he hasn't written them.
The thing is they have already had people been sent to prison for a single "like" in social networks or for expression of dislike in comments section. It didn't look like somebody cared to investigate anything. Something tells me it wouldn't be surprising at all if the "arrested for investigation" is turned into "sent to jail" in this case, too.
They have to make sure he didn't queue up messages to be automatically posted according to a predetermined schedule while he was establishing an alibi away from his computer.