I don't think KYC for airdrops offered is fair for those who joined. Some ICO with airdropping is not also fine to get KYC for tokens worth almost nothing or a burger meal is not really fine. I observed it in some ICOs with airdrops that even with giveaways like that so small needs KYC? Don't fall for it guys, not worth it.
Look at this from another angle. KYC will leave behind all the violators with multiaccounts which eat all your potential earnings in bounty campaigns or airdrops. So KYC is not always something bad. But I think start ups which launch airdrop or bounty that require KYC must tell about this requirement beforehand but not after the airdrop or bounty ends as a surprise for the hunter...