No. This shouldn't even be a question. If we want to say we believe in separation of church and state, then we can't keep blurring that line. The church should not be able to dictate laws, and the government should have no rights or hand in church business.
No -- I know it is part of their job, but it is only a part of it. There are many reasons why some one would choose not to perform a ceremony.... they range from already having plans for the date/time the ceremony is set to take place to not necessarily believing the people asking to be married should be married.
I am sure that the couple could/would be able to find some one that can/will be happy to do so. Frankly, one could apply the idea that if you know the person performing your marriage vows do not 100% support your marriage in the first place, then why would you want them to perform your ceremony to begin with?
Being from a state that just legalized SSM, there has been discussions about this very issue and about churches or pastors that do not believe in SSM and the risk they take stating that fact. Could they be sued? Supposedly not... based on the new law, if they excuse themselves from performing the ceremony due to religious convictions, there should be no repercussions. But, again, why would you want some one to perform your ceremony who believed that what you were doing was an "abomination"? I am sure there are plenty of people in this state that would be more than willing to perform a SSM...