You aren't telling them what to put on their feet, so they ought to keep their opinions on your feet to themselves. Then change the subject. "Thank you for sharing your opinion. Would you please pass the bean dip?"
Or, you could go sassy and just put up your hand in his/her face and then walk away.
I lost whom I thought was a good friend when she discovered I was a barefoot runner. She was so appalled. She even tried to convince me to stop...to save our friendship, I guess. Oh hell no!
My hubby just shakes his head, but then he does that about running in general. On the other hand, he brags on my like mad so at least I know he is proud even if he won't run with me
I am lucky I have a supportive spouse. She sez to my face YOU ARE NUTZ. But I caught her bragging about it to people, "My husband Loves to run Barefoot he is amazing" Gotta love her!
I don't give them the chance, I work hard to exude strength and confidence in running barefoot that they can't help be to be aw-struck! LOL Really though, when you look confident in your actions...others seem to keep their opinions to themselves more. They look for weakness and vulnerability, and if you're out there hobblin along making the whole process look painfully excrutiating they're more likely to stick it to ya. Wear your barefeet with strength and pride and no one can compete with that.
My girlfriend thinks its cool. My parents didn't like it, but I think they are coming around and starting to realize that I'm probably not going to step on a rusted rack of freshly used hypodermic aids needles.