I dunno, I just think both options suck. Yeah, being able to refuse service to gay people could lead down a slippery slope, but so could heavy government regulations on private businesses. Both have crazy extremes that probably won't happen, but might. Jim Crow vs. Fascism.
I just think if a business refuses to serve gay people, in the United States in the 21st century, that business probably won't do too well. I think it's better for it to fail naturally than for the government to step in.