Scott Alexander, at Slate Star Codex, has compiled a handy summary of the evidence for pervasive and socially costly racism and sexism.
I also take Alexander's blog post as evidence of the continuing relevance of the blog as a medium, for four reasons.
1. Blogs offer a longer-form medium than tweets or social media updates.
2. Blogs can be referenced using a stable and publicly accessible URL.
3. It is easier and quicker to publish a piece as a blog post than as a piece of journalism or scholarship in a formal professional publication.
4. Blogs are a convenient medium for people making a contribution outside of their area of specialization. For example, the writer of the Slate Star Codex blog is a psychiatrist by trade, but here he is making a useful contribution to discussions about racism and sexism.