Of course they are against it, they maybe want to stay anonymous and hidden from other peoples.
KYC is required to prevent money laundry and scammers, but i think it is ok for hunters who receiving huge reward.
Yes, the rule about KYC should be announced before the start of campaign, not at the end.
for bounty campaign I think it still makes sense with kyc, but there are some for which required kyc for participants and what they get is also not worthy to be called money. except for the airdrop is really nice and has decent pay.