The two existing answers are great, and are both from moderators in the network. As a mod myself on another site, I'm adding my two cents to supplement theirs.
There seem to be certain things missing in the discussion so far. I added a comment replying to your comment under that post, but soon after the post was deleted, so you might not have seen it.
The spam/abuse flags are not only for moderators. I'd go as far as to say it's usually not for moderators. As you note, the mod team takes time to respond, but moderation is not limited to the mod team. The SE network is in large measure community-moderated. You probably didn't notice it, but the commenter who called on people to refrain from sanitizing the post was not a regular member and probably not even a member of the Japanese SE community. (as a sidenote I think castigation is too strong a word to describe anything that took place in regard to that spam post and the spammer) I imagine that user followed a Smoke Detector warning and came to help spam flag spam posts and keep the community free of spam. Those warnings are pushed to various chat rooms. In fact the two spam posts yesterday were picked up by Smoke Detector: See for example this and this from our chat room.
I left a comment response to yours, explaining that if we modify the post on sight, we run the risk of confusing networkwide visitors following Smokey's warnings here. Of course they could always check the edit history, but then again, everybody's a volunteer and people who are not invested in or familiar with our particular community (Japanese SE) may not go that extra mile.
When the number of red flags (spam/abuse) a post amasses reaches a certain threshold, the system will automatically delete it. The current threshold should be at 6. Please refer to this Meta SE post for more information. That's why the site is community-moderated. (would be nice if we could rid our community of the evils of the SE company)
To sum, I don't think you need to sanitize posts like yesterday's. As you've said, they (there were actually two, not one) were pretty graphic. Such posts almost certainly will get picked up by Smokey and pushed to various chat rooms as warnings. It usually takes a matter of minutes. You know what people say: let nature take its course. Well, nature is us.
On the flip site, I have also seen malicious flag rings in operation—that's a term I picked up from people working on and with Smoke Detector: six socks of the same user viciously attacked another user's post, throwing spam flags on it and sinking it within a minute, right in front of my eyes.