I really don't think Gris was intentionally being mean. He had a migraine. I've had migraines, and it's worse when you have to work through them, when you can't go home and shut yourself away from the world. When I get them, I can't eat. I can't have any noise or sound or light stimulation because it's too much to bear. It's overwhelming. And it affects judgment and mood. You get irritable, you get mean. I've snapped at people I love dearly because of awful headaches and migraines.
I mean, sure, Gris shouldn't have been so rough on Greg, but, A: Gris has been rough on pretty much everyone at one piont or another (pretty much... there are exceptions); B: The stimulus was too much from the noise. He might have just been getting some control over the migraine, and that's enough to flare it up, again.
Grissom was venting. No, he didn't do it in the right direction, but I'm not pissed at him for it because I get that he was in a lot of pain, overstimulated, and frustrated. It's almost impossible to focus and think when you have a migraine. And, here he is, trying to find two little boys, knowing that every second they are gone makes it more likely that they are dead.
I get pissed at Ecklie because he is manipulative and uses people and situations for his own betterment. Grissom was snapping at Greg because he was hurting, overstimulated, stressed and frightened. Really, he was afraid they wouldn't find those boys in time... Grissom snapped because he was trying to save someone, not because he was trying to make himself look better, as Ecklie would do.
I don't think Gris was picking on Greg, or trying to belittle him, or questioning his abilities as a CSI as much as he was just pissed at the world and not handling it the best way because of the added weight of a migraine. Sara got that, and she gently reminded him to treat Greg with a little more decorum, which he did. He was really gracious with Greg when the gasoline came through, and I really don't think Greg did it to spite Grissom, or show Grissom how good he was, or anything. They had a common goal: Trying to get to those kids if they were still alive, trying not to have one more body to examine.
And, I love Alan Tudyk, forever. I want to just watch his face in all the different scenes, because his face is so expressive. You can feel so much emotion even with the volume muted when that man is filling your screen.