Then there's the classification problem. Is post X really about politics? It's not binary.
The only solution that would even approximately work would be to add a block list of domains to peoples' profiles. That way, if you don't want to see anything from paulgraham.com, and I don't want to see anything from HuffPost, we can each do that. But even that only approximately works. I've seen articles posted here that are Twitter comments on Paul Graham articles.
Or, the absolute simplest solution: Skip over the articles that don't interest you. It's really easy to just move your eyes to the next line.