So as someone who goes barefoot habitually and who has studied this, there are no laws that prevent one from going in an establishment barefoot. Yes, an establishment can limit that right, but there are no laws (cite something and prove me wrong). Moreover, why is it less sanitary for you to carry the germs into a restaurant on your shoes vs my soles? There is no difference. Finally, if you're getting your feet cut off in doors, you need to pay better attention.
PS- what kind of goop is on the ground at WDW that is so unsafe to step on? No pets allowed.