Oh I see, you were calling me 'mate' because you think that's a bit of a 'blokey' thing to say. If you'd put a comma after 'gym', your partial sentence might have made sense. I thought you were referring to a gym-buddy. If you could possibly write in complete sentences, that would help.
I think what you must be saying is that I must be a man, because I don't share your views on sex discrimination against men. Please correct me if I'm wrong. Can you see how illogical and offensive that stance is? It would be like me saying you must be a lesbian because you hate men.
I've copied an pasted the appropriate logical fallacy for you from the BBC's website, to save you having to Google it. Hope this helps.
"Saying someone "must be a man" simply because they disagree with a specific view on feminism is an ad hominem (specifically an ad feminam / circumstantial ad hominem) and a genetic fallacy"