It looks like donations may not go specifically to the Kleins...
“If you want to help Aaron and Melissa and other Christians deal with blatant discrimination, make a donation to our “Persecuted Christians—USA” fund below.”
Thats probably the best way to do something like this: have a religious organization set up a general fund to provide relief for people like this.
It may cost more because of gift tax law. But the minute GoFundMe or any other similar organization cuts off the effort THEY can be sued for religious discrimination.
Lawfare works both ways.