Why do you blame Binance for the price drop of Luna?
Binance is an exchange and they have their own T&C on how they will delist a coin or token. But, if this is about the price drop, do you only get this once on Luna? Wake up dude, there have been so many coins that are dropped with extreme drops so far in many exchanges. Not only in Binance.
You know, Luna is traded in many exchanges. If Binance should delist every coin that is dropped, all coins and tokens in Binance should bedelisted at all. are you kidding?  
See this:
https://coinmarketcap.com/currencies/terra-luna/markets/