He could be a white surpremesist. It would be a conflict as he is gay, but people can still believe anything they want.

You say the tattoo "resembled" and was on his chest. This means that you dont know for a fact the symbol was what you interpreted it as. He very well may have not seen the connection. I know there are many symbols related to gangs and beliefs and such that I am unaware of.

Accept that you dont know and give yourself permission to move on. Seeing a therapist may also be a good idea.