I see where you're coming from. In my opinion the search engine shouldn't take a stance when it comes to politics, though. They claimed they only step in when it's illegal content or copyright, but I haven't seen any evidence of them removing left-leaning sites in this fashion.

I can't prove that what Google did specifically targeted Breitbart but if it was just changes to the algo then we should have seen other popular sites with similarly dramatic drops in visibility. I'd love to see other examples if they do exist