The Prime Directive
One does not give a TARDIS nor the power of immortality via whole body cell regeneration to a species to which people such as Adolph Hitler belong nor even risk bringing such things near them, and neither does one teach a class on ethics to a swarm of locusts.
This is the way.
This is the sad reason that welcoming Aliens are not going to land on the Whitehouse lawn.
We suck, let’s deal with it.