On Being Called Transphobic Simply for Not Believing that an Individual Can Magically Change His or Her Gender

I have zero problem with trans-people and support equal rights (I'll even call a male to female tranny, she, if it makes HER happy) but I will not concede that an individual who was born a male (i.e., a human who's only non-Y chromosomes ironically reside in his sperm cells) can suddenly become a female simply because "he" undergoes a series of surgical mutilations, dangerous hormonal therapies, mental gymnastics, etc.. Sorry but that's a bridge too far for me.