I would be especially careful of arguments that end up like "it's a great opportunity for humankind as no-one else is there to compete for the next million year

I would be especially careful of arguments that end up like "it's a great opportunity for humankind as no-one else is there to compete for the next million years" It might be true. But the most likely thing we will find on the nearest habitable planet is a legal writ and summons.