I think MN does have a left wing bias. And yes, in general social media is disproportionately left wing compared to the population. Twitter is more left wing than Facebook, but still more than the population - mostly due to an age bias.
I'm a Tory and mostly lie low as I'm sick of being called a cunt. I've tried to have sensible debates but they always deteriorate into mud-slinging.
As soon as someone starts swearing and name-calling they lose my respect and I pretty much assume they're ignorant if they have to resort to profanity rather than proper words to make their point!
The problem with just posting endless links to 'facts' supporting your point of view is that they can nearly always be refuted with an identical set of similar 'facts' supporting the opposite view. I'm happy to research things and form a point of view (and change it if necessary) but I haven't the time, or inclination, to justify it with a bunch of strangers who just want to spam the board with their angry rants.
I have a degree in Economics and could wax lyrical with a reasoned debate as to why Jeremy Corbyn's manifesto hasn't got a cat in hell's chance of being deliverable, but in an age when experts are derided, what's the point?
I'd much rather have a civil, grown up debate with people in real life - as I did with some friends last night. We didn't agree, but we did concede elements of each other's arguments, and at the end of the day we hadn't changed our minds, but we were still friends!