If you feel so strongly that the planet needs less people, then why isn't it ethical to kill some of the excess ones? Justify it as defending the people you lik

If you feel so strongly that the planet needs less people, then why isn't it ethical to kill some of the excess ones? Justify it as defending the people you like from whatever effects you think "too many people" are causing. Having decided that "too many" is the call (and that you're the person to make that call), would it be better, ethically, to leave that distasteful task of cleansing the undeserving to someone else? *what if they don't have the same notion of "undeserving" as you?