So, his letter of that alphabet--which define his sexual preference--is 'Q'. But he doesn't accept that designation, or others common terms associated with the community for himself, like 'coming out'.

The Sigma/Zeta thing though is a bit surprising to hear.
On my campus I remember a large amount of both also being members of the LGBTQ community. I thought their apparent acceptance of that community was a reason why members gravitated to both of those orgs.