If the cheapest flower shop in the county refuses to do service with Adam because he's gay, Adam hasn't chosen to do business elsewhere; he was forced to. That's the definition of burdensome.
Are you saying that because alternative businesses might be easier to find in some cases on the internet and in other places, it does not create an undue burden on someone discriminated against? Can you speak for all goods and services in all places? In small towns, like during the era of Civil Rights, will Adam not have to drive 50-100 miles for a comparable business or service? What if it's something Adam needs right away that his straight counterparts could get but he couldn't?
Regardless of alternative availability, do you know what undue burden means? An embarrassing discriminatory event followed by a ten-minute drive to an alternative business is legally an undue burden.
Discrimination shouldn't exist for obvious reasons, including the ones I've listed.
Actually, many of the practical effects of institutionalized racism were killed by policy, which eventually led to social change. Large-scale social change didn't occur until after businesses were forced to accommodate all groups equally, schools were forced to accommodate all groups equally, etc.
Foxi4, we've respectfully disagreed in the past. I've even empathized with some of your positions. But in this case, respectfully, your reasoning is idealistic cherry-picking that doesn't make sense.