 Why is the Sand God causing a terrible storm?
The sand-thing was powerful, lonely and strange. He touched the pencil-line scar behind his ear where the cylinder was buried, marveling at the power stored there, power to fling him from earth to this fourth planet of the Centaurian system in an instant. A gray, funnel-shaped cloud of dust stood off to his left. He watched it, trying to recall what he might know about cyclones. Weather control made cyclones and other climatic phenomena on earth practically non-existent. The cloud did not move, though, except to spin on its axis rapidly, emitting a high-pitched, scarcely audible whine, like a high speed motor. He stood on a wide valley floor between two mountain ranges. Dark clouds capped one peak of the mountains on his left. The sun—no, not the sun. He was here and Earth was somewhere up there. The sun burned fiercely, although he would have said it was about four o'clock in the afternoon, if this had been Earth. The funnel of sand had moved closer and while he watched it, it seemed to drift in the wind—although there was no wind. When he looked up the wind devil was there before him. The sun shone obliquely, throwing Stinson's shadow upon the sand. The wind devil also had a shadow, although the sun shone through it and the shadow was faint. He was here to investigate, to determine if this planet was capable of supporting life. He examined the wind devil as closely as he dared, but it was composed only of grains of sand. But then, how could a group of loosely spaced grains of sand possibly have a nervous system? When it changed to a cube he drew a square, a circle for a sphere, and so on. He became so absorbed in doing this that he failed to notice how the wind devil drew closer and closer, but when he inhaled the first grains of sand, the realization of what was happening dawned with a flash of fear.
 He is angry because he doesn't understand Stinson.
 He knows he can't control Stinson.  He is angry because Stinson figured out he is a child.  He is angry Stinson took Sybtl away from the webfoots.  He is angry because he doesn't understand Stinson.