They already have enormous political power, so I fail to see your point.
...that was my point. Your argument is that to fix the issue of churches interfering with politics and attempting to influence the government, we should force them to take part in gay marriage or remove their tax exempt status. How in the world does that improve the situation? Who does that benefit in any way?
With gay marriage now legal everywhere, and with zero chance of getting enough states to approve an amendment to the Constitution banning it, it's the time to use this as the impetus to remove churches from the political process. Keep your tax exempt status and extricate yourself from the political process so you don't get muddied up by the taint of immorality as law.