Disrespect is everywhere and I learned to ignore it, my own grandpa used to do nothing but speak ill about my kenpo sifu. I used to get angry about it by then I realized why should I care? The results have done nothing but proved he does know what he is doing and is a great teacher.
My cousin once picked a fight with me in a home depot by slapping me across the face, so I kicked him in the mouth and busted his lips. Since then he never did that again.
These are all cases of ignorance, they assumed I was weak and my style did not work. Many non martial artists think MA is all just a scam until you show them or they find out the truth for themselves.
Disclaimer, don't go around beating these people up. You might prove MA is not bs, but you'll also prove you're an *******.