Anyone who would impose such conditions on a host should be asked to eat before arriving, or be uninvited altogether.
This isn't like the vegan freaks, where their weirdness is totally voluntary, but enough.
I don't understand why anyone would include themselves in a social setting, knowing that their presence makes the others uncomfortable.
We all make mistakes, I have brought an expensive bottle of wine to a dinner to find out all the guests were of a faith that did not touch the stuff. How the heck are we to know if an host is Baptist or Unitarian.
These people sound concerned for the comfort of their guests, but are going a bit over board with it.
I always locked up my dogs when a Muslim coworker came to visit, just manners really. I also removed my shoes when entering an Asians home, no big deal, just manners.
One thing I learned the hard way, never go to a Russians home with cheap Vodka and never get the flavored ones, Sacrurigeious act