So a homosexual who slips and has sex with a woman (and many do as evidence by the number of children who have gay parents) needs to be declared straight for life. If a = b, then b = a.
Nope, a=b then b=a does not apply here, you can be a bloke who has built many walls and be called a wallbuilder, many houses and be called a housebuilder, but as soon as you have sucked a cock you will be known as a c0cksucker and never a housebuilder again.
Once a phegget, always a phegget.