The issue with something the sheer size of reddit or facebook is that whatever your stance, you can be absolutely deluged with thousands of people who feel the same. Everything is just way too big for anyone to be exposed to all of it and get a fair assessment of the stance - ultimately we now rely on algorithms and karma systems and other things to do that filtering for us, and these systems all have their inherent flaws.

Accept that in any system large enough, you will never get a fair assessment of what the majority of people think. And even if you could, what would it matter? Each half of a divisive issue that splits reddit is big enough to go and make its own system, which would still be so big you'd not be able to tell the difference from the original.