Yes, people shouldn't be denied service because of their sexual orientation. I know this is just a birthday cake, but there are some towns that only really have one market for the whole town. If that market was allowed to refuse service to gays, it could force them into becoming subsistence farmers or travel long distances just to buy food! That would be crazy.
Basically this.
Using religion to justify discrimination is disgusting. If history and the current trajectory of this country are to be trusted, this bs will be banned eventually and these assholes will have nothing to fall back on.
Thankfully, many of the fiercest grass roots support for advancing civil rights came from deeply religious groups who used their heartfelt religious beliefs to spread love rather than hatred (groups like the Quakers were some of the first abolitionists, Black churches organizing civil rights marches in the South, etc.).
Agree completely with Siren's post.