I would hope, in this case, the government wouldn't be influenced by the Church. No one has any right to change a person for who they are just because someone doesn't think they are right with who they choose to spend their lives with.
This would put homosexuality in a group with other things like Aspergers and ADHD. Of course, parents have the legal right to administer drugs to control these things.
Another question is (if the drug has no effect on heterosexuals), would we be seeing parents administering said drugs before any signs of homosexuality appear as a "just in case" cause? Should such drugs ONLY be allowed to be administered to people once they are over 18 and not parents? Would parents feign homosexuality in an effort to get said drugs to give to their kids?