A lot of web filtering software employed in organisations is automated, and among other things is based on the meta tags used to describe the site to search engines.
If a site has words in the meta tags which are the same as other sites which contain inappropriate or pornographic content, such as 'sexuality', for example, then it will be blocked. Nothing to do with discrimination or censorship. After looking at the source code for the main page, there are several meta tags with the word 'sex' in them. This will likely be the reason.