Sin is sin. and IF being gay is a sin, then no-one who sins is fit to judge on that premise

I may be misunderstanding you but it does seem to me that you do believe there are sins. Let me pick on something I would feel confident that you would believe is a sin and ask you:

If you believed theft was a sin, would you be sitting in judgement by stating your belief? Would you be sitting in judgement by not wanting be an accomplice to theft?