Some ICO's are bound to implement KYC's due to strict restrictions and terms. About their legitimacy, maybe you can spend more time to research if they are really a legit company. There are ways to verified their legitimacy with the proper tools and recommendations that we can discuss on other discussions.

Anyways, airdrops are supposed to be not restricted at all. In my whole experienced of playing in a new alts, I've never seen an airdrop asking for KYC.

Can you tell us what Airdrop is that and linked their ANN thread here if available?