(a) not to dismiss HN as a bastion of racism and sexism, as doing so concedes the whole site to those ideas
(b) to challenge racist and sexist arguments on the site both reliably and civilly.
Most of the people putting those arguments forward are trolls, and are seen as such by the site (watch what gets flagged). One of the most effective strategies race and gender trolls have is to rile up thoughtful people so that they make dumb, angry arguments. It creates a kind of autoimmune disorder on the site. Don't enable them.