That's nice, but in the real world same-sex couples sue bakers for specific performance.
This isn't the Civil Rights movement in the 1960s South. Bigot enslavement is not an appropriate remedy, especially since personal services and non-fungible goods are usually exempt, and specific performance isn't necessary in most of these discrimination cases. Furthermore, homosexuals should have the right to refuse bigoted religious customers.
Anything that restricts the law of specific performance is in our best interest, even if political hacks feign Christian virtue to appease their constituency.
As you indicated in your original post, specific performance is just a type of remedy, not a cause of action. Its availability or unavailability in specific types of lawsuits has nothing to do with this Michigan bill. The bill would prevent gay couples from bringing discrimination-related suits seeking monetary damages or any other type of relief.