If it was being used to harass or as part of their harassment of another player then they've not been banned for spamming holy. Spam is one method people use to troll, which for example, is a common method used by people who troll RPers. In that context, I think punishment is necessary. It can be very disruptive of things like RP.
And sure it could have been nothing too bad as far as harassment goes, but why go out of your way to be an a***? if that catches up to you, then it's your fault for being an a***. I don't think the punishment was even harsh, the guy couldn't play the game for 3 days, it's not like its a long or permanent ban.
The intent here is the problem, not the action. People who followed the reddit side of this story established that this guy was harassing somebody who asked them to stop. If people aren't going to stop harassing you then it's acceptable for them to report for harassment. If the person has previous offenses then of course their punishment will be harsher, which was the case, else he might have just got a warning.
At the end of the day the GM's have to discourage bad behaviour, players who go out of their way to antagonise other players rightfully should be discouraged because that is bad behaviour and I expect SE are against it because if they held a lax stance it'd create for more of a toxic atmosphere, which is what happens in communities where it is more lax. No matter how big or small you think the action was, that's what the player seemingly was doing judging by the rest of the story. GM's can warn against it, but if they are a repeat offender and this guy was, then don't be surprised that they follow through.
But it's really easy to avoid this kind of result. Just don't go out of your way to antagonise people.