My sense of the issue for ministers is a bit different. We are “licensed” by the state to be “legal” solemnizers of marriage. No place on that license that I can see does it say anything about who can/will/must be married by that licensed pastor. I would say, then, that even though that church might not be forced to conduct a homosexual marriage service that the license of the pastor to be a ‘legal’ agent of the state can be revoked for not being an available resource.
To avoid this sad scenario, it may come to the church having to drop the pastor's being a "legal" agent and having both a civil servant (e.g. judge) and a minister co-officiate at a Christian wedding. Of course, this is what societies such Soviet Russia did when Communism prohibited religion. The Christian service was conducted in private away from the prying eyes of the KGB. Is this what American Christians have to look forward to to avoid the state-sponsored homosexual gauntlet against Bible-based Christian religion?