As said, there's no way any 'airdrop' can 'hack' 'myetherwallet' (alot of ' because it's not giving the full clue about what it is
)
Anyone can send tokens/ETH to your wallet, with or without your consent.
You can't in any way possible lose your tokens/ETH by receiving tokens.
If you're filling in your private key in some suspicious site, then that's why you/people lose their stuff when joining an airdrop.
There is rarely reason to enter your private key anywhere.
MyEtherWallet is only an interface that makes it much easier to 'talk' with the Ethereum blockchain.
MyEtherWallet could be hacked in the terms of like a DNS hack that happened recently,
which I believe kinda redirects everyone who visits MyEtherWallet.com, to a fake site, that would then steal your private key.
MyEtherWallet could also be 'hacked' in terms of someone changing the code to save your key, I guess, why not?
So to summarize, you are just as safe using MyEtherWallet as you are using any other type of wallet which gives you the same access(private key access).
However, using MyEtherWallet and being an unexperienced internet user in terms of any safety aspect, is definitely more risky than using for example a Hardware Wallet,
or even an exchange with 2 factor authentication. I don't promote using exchanges at all, but it's safer as it kinda protects you against yourself.
MyEtherWallet gives you a Public Key, and a Private Key(maybe in form of an encrypted file, or another option).
Whenever you visit MyEtherWallet to login, you risk actually entering a phishing site.
Ensure that you always see the green lock icon in the top left, bookmark the url, and so on.
Your Private Key from MyEtherWallet however, isn't MyEtherWallet-specific, it's just a private key tied to a public key on the Ethereum blockchain.
You can use it in many other ways other than via MyEtherWallet.
Simply put, you can't lose your money unless you fail on your end, one way or another.