You absolutely have the right to refuse, it just means that your gun or you don't get fielded there. Their house, their rules. If in fact they are adjusting the hops on players guns, that isn't too smart, but it certainly isn't malicious.
How'd the Hop get destroyed, was something other than normal function being done? Did they adjust it with a hammer or something? There's plenty of ways for things to break, but was it a rubber, the housing, from adjusting it, from shooting it, etc?
It doesn't matter, if they want to test with hops off, then they can test with hops off. Best thing to do is to turn it down before you get to the chrono, get in there early so you can go re-adjust before the game.
ďREALITY IS LIKE A STONE. TO MANY ITíS HARD AND COLD, THEY CANíT HUG IT OR EAT IT, IT ONLY FRUSTERATES THEM AND DOESNíT DO THEM MUCH GOOD. TO OTHERS ITíS STRONG AND DEPENDABLE, YOU CAN BUILD WITH IT, BUILD UPON IT, OR WORK WITH IT, ALSO USE IT TO SMASH PEOPLE IN THE FACE.Ē