Would Plato lie? Sure, he's only human. Lots of people find it hard to follow their own ethical principles. But is the Gorgias so deceptive that Plato couldn't have fooled himself into thinking it was okay? Because clearly Bruce McComiskey is right about the real Gorgias being less likely to assent to everything Socrates would have said. Gorgias was an accomplished rhetorician, so even if Socrates caught him in a few contradictions, it seems he would at least have had a better response than "Apparently" any time that Socrates asked him a question that would make Gorgias look stupid. Like a modern politician, Gorgias would likely have refused to be backed into a corner with a yes or no question, preferring instead to simply state his beliefs in his own words, perhaps even putting Socrates on the defense rather than letting Socrates control the debate.
I find McComiskey's argument unconvincing when it portrays Plato as willing to do anything to stop the democrats. I can accept that Plato strongly opposed democracy. But how involved did Plato really want to get in politics? Did he see the Gorgias as a rhetorical piece, designed to persuade people, or did he see it as a philosophical piece, designed to demonstrate truth? I simply don't see enough evidence to believe that Plato wanted the Gorgias to be rhetorical to see him as misrepresenting sophistic arguments in order to see the end of democracy.
What seems most likely to me is that because Plato saw truth as being singular and universal, he believed that sophists really would have to assent to Socrates's arguments (if they listened to him and let him set the terms of debate). If they answered yes or no questions reasonably, even sophists would have to agree with Plato.
McComiskey, Bruce. "Disassembling Plato's Critique of Rhetoric in the Gorgias (447a-466a)." Rhetoric Review 10.2 (1997): 205-216.