He needs to realize two things.
1) As a buisness owner discrimination against someone's sexual orientation actually is in contradiction to the Equality Act and therefore is illegal. This was upheld by the State of Washington. So sure, open the door for lawsuits. I am sure that those lawyer expenses will do wonders on his expense ledgers
2) The freedom he has to practice his religion stops when he is trying to impose them upon others. He is providing a public service as a buisness owner. He losses the right to say he will refuse to serve anyone, based on that. 

He also needs to understand that individuals in the community can also ensure that others are made aware of his bigotry and refuse to  patronize his buisness.  And if it goes under, I would shed no tear. He can then enjoy explaining to his creditors why their investment went under. 

And for those that say he has a right to serve whomever. Replace gay with African American or Hispanic, and ask yourself does this sound bigoted?