According to the ban list, he was banned for trolling.
The length of the ban is in accordance with the number of active infraction points that MR had when the ban was given. More points means a longer ban. It's not that hard. The policy is clearly posted for anybody to look at it. If you haven't, then go to the "Site Feedback" forum and take a look.
This site really needs to decide what it wants.
A pure science site would never have a section inviting posts about Ghosts and Monsters.
This site, it seems to me, is a mixture of popular science, current affairs, general chat, and fringe science.
There are no Nobel prize winners popping in to discuss their latest discoveries.
If you are going to have a ghost and monsters section, which is very popular, then you need to get to terms with what that involves.
You are going to attract posters who actually believe in the stuff.
I believe that 90% of MR's views are nonsense.
But he is a clever, amiable and interesting poster.
I like arguing with him occasionally.
He also posts prolifically.
If you want the site to be successful as the kind of forum sciforums actually is, then he is a person to be encouraged not banned.
Where was he trolling?
What's trolling anyway?
If trolling is having a viewpoint that people argue with, and putting it forcefully, then that is also a positive.
If you want people to contribute and argue, that is.
The best people we've got on here are all trolls.
Please. Make up your minds about what you want.
If you don't want fringe science, don't have fringe science sections.