Liberal users comprise a larger percentage of these r/politics users, while conservatives will comprise a smaller percentage. Through those users and through their voting, they can control what is seen and what is not seen. So a liberal user, as a block, will downvote more often than not something they don’t agree with necessarily.
r/science is really the largest science forum on the Internet. We say that we have more than 18 million subscribed users. For a point of reference, the total combined subscriber base of the top ten newspapers in the United States is around ten million.