Fact 1: Earth's supply of oil, metals, fissiles and rare earth minerals are finite, rapidly being expended and already insufficient to provide everyone with a first world quality of life.

Fact 2: Without said materials or hypothetical Outside Context technologies we don't possess or even have the slightest clue as to how we might create, a space program is impossible.

Fact 3: In the long run, the extinction of all life on earth is inevitable, on account of the sun going red giant if nothing else.

Fact 4: If humanity doesn't have a breeding population offworld by then, that includes us.

Conclusion 1: If we don't get off earth soon, while we still possess the material richness to do so, we never will, inevitably leading to our extinction.

Conclusion 2: This means that attempting to sabotage attempts at getting off earth can be considered an existential threat against the entirety of humanity, therefore morally justifying anything done to the saboteur/s as self defense.

Much as kin selection demands I hate the trisolarans, I've still got to admit they've got their heads screwed on right about how to appropriately deal with traitors to their species.