Barefoot Is Legal: People Offended By Feet

Why is it other people's business when someone removes their shoes (or does not wear them?) If people say they are offended b seeing someone's foot under a table or chair, why are they staring at them?
If someone wears socks with sandals, why is it not okay to say something? What if you do not like someone's facial hair or the shirt of someone else's favorite sports team?
http://www.barefootislegal.org