I personally think that it is rude for people to force guests to take off their shoes when you invite them to your house.
what if they have smelly feet, holes in their socks, or ugly feet and feel self conscious about them? you don't want to make your guests feel uncomfortable. if they want to take them off thats one thing, but don't give them an ultimatum.
As far as i can tell the person who made this sign is an Asshat.
that is all.