I heard at least part of that story before, and continue to be flabbergasted that anyone could accuse you, of all people, of being phobic and discriminatory towards any aspect of sexuality, gender or identity.

I can see a bit of a conflict - if the slogan bothers some people, should it be used? But not using it would appear, at least to the bullies, that they "won" and therefore give them additional motivation to keep up that sort of behavior. That's a hard call to make, and I think walking away was probably the only reasonable option. What a poisonous environment, and over something purporting to do with love!