That's honestly the best reason he has given for it so far.

If that even made sense, it would be even more reason to deny him it.

Someone throw some green-painted dirt on his face and tell him "Here's your greenland, now fuck off"

At least he is honest...

So, he understands the concept of a safe space... But only for him? And only if it's... a country?

Surely the intelligence agencies at work in sane countries are considering assassination operations, right? Isn’t this like the most worthy reason to attempt such a thing, threat of global annihilation?

Psycho for sure but totally illogical

The US already has direct colonial control over NATO. NATO is fully committed to not let Russia invade Greenland or setup oil rigs off the coast, and it is absurd to suggest that Russia or China are patrolling Greenland or have any desire to attempt to take their resources without cooperation. But the US would get NATO's help for defense of Greenland, and NATO would permit greater US contribution to NATO command bases there, or obey orders to contribute more themselves.

Trump, in addition to repeating the false China/Russia threat, has admitted zero interest in Greenland's resources. They are too far away and extremely expensive to develop. This leaves only a single possible motive for needing US control over Greenland: The absolute certainty that EU will disobey US orders for greater submission and the need to directly threaten them from closer distance. There is no offensive missile threat to Russia provided by Greenland relative to other NATO territory.