Megatron actually laughs. He's certain he knows what Starscream is talking about, and that interpersonal weakness is one he's much more capable of looking at with a self-critical eye than his whole sordid past and present with Starscream -- probably because he considers his embarrassing overblown rivalry with Optimus Prime to be squarely in his past at this point, whereas he absolutely still hates Starscream and considers his attitude towards him to be objective and reasonable.

"Oh, yes -- just get Optimus Prime out of the way and you'd already be constructing a Decepticon utopia. With your Commander Megatron at its head, of course, and any and all dissent crushed by whatever force he deems necessary, because he's right and anybody who disagrees with him just needs to see reason."