The same reason John didn't push Rodney that much in "Tao" - because if he yells at Rodney to fix it, then he's acknowledging that Rodney is going to die. If he just relaxes and pretends it's a regular day and they're just out on a picnic, then he doesn't have to think about Rodney dying. And something will come up to save Rodney in the meantime, because something always does, because Rodney is not going to die.

...Umm, I know this sounds utterly contradictory, but this is how I think John's head works. It's a scary, strange place, inside the mind of a Sheppard! (I'm tempted to try to fic this scene from John's POV, maybe see if it would make more sense from the internal perspective?)

But we've never once seen John just accept a teammate's death before, under any circumstances; I cannot imagine that he would've started now.