Anything not-pro-clinton gets downvoted without explanation on any social media platform I've seen, including HN (which is supposed to be less biased, more objective, and superior to the other networks).
Personally I have not noticed any particular bias here except for at backing up assertions with some facts.
* Both parties have worked hard to polarize the population and make this election the most divisive ever.
* In the case of HN, your audience is from a most progressive or libertarian background, who have no love for most of the conservative agenda
* In the case of Facebook and Reddit, the Clinton campaign is paying people to bury any criticism of her. (Correct The Record)