So expressing contrarian opinions is grounds for banning?

As always, it's a matter of degree and interaction on how well argumented your position is.
So yes, you can express a sufficiently contrarian opinion that would lead to banning. "All women should be treated as sex slaves", for example, is such an opinion.

Except he did explain why he believes what he does.

I asked aa at least twice, possibly more, what evidence he had for his assertions and got nothing back. Can you point me to a place where he did so? A post mortem would still be useful.