Innocent question about Heinlein's Green Hills of Earth

[james_davis_nicoll]

(Poem quoted from Atomic Rockets)

Let the sweet fresh breezes heal me
As they rove around the girth
Of our lovely mother planet
Of the cool, green hills of Earth.

We rot in the molds of Venus,
We retch at her tainted breath.
Foul are her flooded jungles,
Crawling with unclean death.

[ --- the harsh bright soil of Luna ---
--- Saturn's rainbow rings ---
--- the frozen night of Titan --- ]

We've tried each spinning space mote
And reckoned its true worth:
Take us back again to the homes of men
On the cool, green hills of Earth.

The arching sky is calling
Spacemen back to their trade.
ALL HANDS! STAND BY! FREE FALLING!
And the lights below us fade.

Out ride the sons of Terra,
Far drives the thundering jet,
Up leaps a race of Earthmen,
Out, far, and onward yet ---

We pray for one last landing
On the globe that gave us birth;
Let us rest our eyes on the fleecy skies
And the cool, green hills of Earth.

By contrasting the habitability of Earth with the harsh, inhospitable conditions in space, is Heinlein undermining the crewed space cause?