My answer, is nothing at all. As follows.
First, _given_ the (false) view of homosexuality as a sin.
"Hypocrisy is the homage vice pays to virtue."*
The minister is a sinner (in this context). Nevertheless he honors virtue (heterosexuality). His sin is his own problem. His public actions (attacking sin) are not affected by this.
Second,_given_ our (true) view of homosexuality as a legitimate form of sexuality, it is incorrect to expose or pass on the exposure of any gay person. It is politically toothless because a minister's hypocrisy does not in itself call in doubt his political position. Hence no political point has been made but a gay person has been caused additional misery with no benefit accruing to the cause of gay liberation.
Carrol
*If you google this you will find several rebuttals of it.