Well, politicians must be told to not to bring religion and personal views in account while making judgements because that promotes bias. And this is something that no good leader would let his judgment get clouded with. Furthermore, condemning someone’s sexuality is usually always a matter of ad hominem.
This is when a person runs out of constructive arguments to give, so he resorts to personal bashing. Pointing this out in public could usually always spark a thought, and can prevent the politician from resorting to such an argument again. The best way to respond however, is through an open discussion regarding how bible does not really condemn homosexuality.