I think this discussion touches very different points.
First there is the thing about spam releases. I think if somebody just creates a fake entry in MB things are clear: it is not backed by any data and should be removed. But we also had the discussion some time back, whether a release that was seemingly only created to be included in MusicBrainz, but the release existed . Most people agreed that it should be allowed, since it is an existing release with actual music (at least audio, people disagreed on the term music in that case). But that's a difficult case, and it probably can only be decided case by case.
The other point are illegal, immoral or banned releases. My point of view here is, that MusicBrainz's job is to collect data about music that was released. It is not MusicBrainz's job to judge the value or morality of the music, it should collect facts. Music is banned and censored worldwide for a wide range of reasons, and the reasons change both geographically and over time. What might have been completely acceptable on the release date would be considered immoral or even illegal today, and vice versa.
Whether this view is compatible with a certain jurisdiction or one's personal morality is a completely different matter. So having some way of reporting releases and marking those releases in someway might actually be a good idea, but I think it should be up to the user whether they want to get the releases filtered on that criteria or not.
 Has somebody a link to this discussion? Can't find it anymore