While I agree Reddit 2015 does reflect more of the US mainstream, it is still far from being an actual reflection of popular US opinion. Reddit is far more atheist/libertarian than the US mainstream. And I would argue it is right now far more reactionary/right wing as well. It has become very popular among young white males who have unhealthy attitudes towards women due to the abundance of porn and generally retrograde attitudes towards women of Reddit in general (both the users and the site itself.)
Same goes for its attitudes towards race.