It's called a rider. All bands have it in their contract. Don't be so naive and try and make it out to be a political gesture. It's not. It's part of the gig. Some bands ask for clean socks. You can easily find bands riders' on t'web, just look. The most famous is for m&m's with the brown ones taken out (I think it was to check if people actually read the contracts).
Chumbas are good, solid, fun loving, very intelligent, caring people. Don't make out they're not.