MN isn't really left-wing at all, nor is it particularly right wing.
It is more that there are a lot of vocal posters that hold views that you could describe as being the perspectives of the modern "liberal establishment", a bizarre and rather self-serving mix of internationalist and social justice ideals that, in reality, have rather strict parameters on the ground, along with the incorporation of right wing ideas such as the sanctity of private property and individual privacy and agency.
These have become associated with being "left-wing", probably because these views infected the Labour party under Blair and the left wing of the Tory party under Cameron. They also form the bedrock of what people perceive to be "BBC bias", and this is why the left thinks the BBC is right-wing and the right thinks the BBC is left-wing.
What is truly bizarre at the moment is the extent to which people that adhere to the principles and ideas of the liberal establishment are moving towards support for Corbyn. Corbyn is a 1970s international revolutionary socialist from a privileged background (surprise!
) whose fellow travellers (Milne, McDonnell, Murray) are even more radical (ie. supporting vastly authoritarian measures) than he is. These are people who think Stalin was the best thing since sliced bread; if they were on the "right", they'd be Nazi apologists.
At some point, the reality is going to dawn on some people that the sheep they favour aint a sheep at all. That should be somewhat fascinating. Interestingly, the only people that are trying to expose all this are those on the non-authoritarian left and the old traditional (methodist-ish) Labour left.