I know that this is not a direct solution, but I wanted to offer it in case a Plex Plugin doesn’t surface soon.
My solution would be to use XBMC to build your porn library and metadata. They have an adult plugin repository (https://github.com/xbmc-adult/xbmc-adult) which includes a scrapper that uses AEBN’s gay movie section. That would probably be the largest gay porn database for pulling metadata. Depending on your specific tastes in porn, it may not be terribly successful.
From there, you can export the metadata from XMBC to Plex. Use this link for reference: https://forums.plex.tv/index.php/topic/38402-metadata-agents-for-exported-xbmc-library/