A tautology is when the two are the same by definition, I think you mean that there is almost complete overlap.

No, I mean to say that "major issue of contention" can mean in the US that it's a topic where there contention between the two major parties.

Which is something I still disagree with, as in cases of for example gay marriage, the general populace was much more in favour than you would guess from listening to either political party.

Latest gallup poll indicates 52% to 43% for the general population approving of same sex marriage. I don't think that's far of what y

The issue I have is with the tendency to upvote posts that show both sides of an issue as being equal regardless of whether or not this is actually the case.

Could you give examples? I personally haven't observed that pattern on LessWrong.