Do I have grounds for a discrimination law suit if my company will not let me start a queer club?

Possibly but I'm not sure you have monetary damage to recover. The denial of the club probably isn't what we call an "adverse employment action," such as a demotion, pay reduction, termination, denial of raise, or forfeiting benefits. (It didn't cause you any monetary loss.) A court may consider injunctive relief to compel the employer to allow a social club, but the employer would have the opportunity to explain itself and defend its position. Absent monetary damage, getting an attorney to sue on contingency is unlikely unless you have identified several (no specific number but more than a handful) coworkers who are interested in the club to bring a class action under state law.