Baloney.
If you go into a store and they don't have the product or service you want, you go somewhere else. You are NOT being 'put on the fringe.'
There is a store here in town that sells sport clothing. Nothing for women above size 16 and THOSE sizes are put waaaay back in the back of the store.
Why can't someone who is a size 18 sue them? Are they not in business to sell sport clothing? This person who wants a size sixteen wants it to work out just like the person next to her who happens to wear a size 6. They go to the same gym, participate in the same marathon events, hike together...but the size 6 can get clothes there and the size 18 cannot.
How is that different from the baker? Because this clothing store is quite obviously discriminating against people he doesn't approve of; heavy people.
But that's just fine, isn't it?
The size 18 is just going to have to buy her clothes somewhere else, isn't she? Nobody is going to force this guy to stock larger clothes, or force the seamstress there to let out any seams.
I don't see a difference.