As long as some placement agencies will work with gays they aren't denied the service.  To require all agencies, including Christian agencies for whom homosexuality is rightfully counted as a sin, to deal with Gays is religious persecution.

There are a number of cases where Gays have used Gay marriage as a club to beat down Christians even when other alternatives were available.  A Christian Church was prosecuted for refusing to perform a gay marriage even when there were other venues available.  Christian parents have been arrested for pressing for their parental and religious rights to teach their children that homosexuality is a sin. 

As long as there are agencies that Gay people can pursue adoption through there is no need to force Christian organizations to abandon their principles.  Religious freedom was one of the highest priority issues in the Bill of Rights.  Religous Freedom is crucial to the moral fabric of our society - crucial to the survival of civilization.