What's unrealistic about this scene? I'm sure any teenager would act the same way when faced with a mounted turret

Yeah it's definitely not an objectively good show, but something about it makes it easy for me to turn my brain off and enjoy it for what it is at face value. It's probably the fact that you don't often see media justifying violent resistance against a country that's somewhat of a stand in for both the United States and the British Empire. At the very least it has an anti imperialist slant

I wouldn't call Code Geass liberal, they explicitly are anti-empire and show the people saying "maybe empires can be talked down" are wrong, and show realpolitik trumping liberal politics every single time. Lelouch completely disassembles the social set up of the empire and a lot of the class inequality, and that ends the military drive so they turn inwards and fix problems. Suzaku is the most liberal character and 90% of the show tells him he's stupid and wrong. The most liberal part is with Euphemia, an characters say her plan wasn't going to work in universe, so it's not like the writers try to convince you she was right in every way. It also worth noting a lot of his fighting strength in the Lancelot comes from the fact that it is just an absurdly fast mech, that's why he can overpower everyone else. He's the only one who could pilot it because the has really good reflexes, which is really not that much of a stretch. I would say the amount of fancy mechs towards the end of the show gets annoying, and they start pulling more ex machinas of either sort to make the plot happen after the go to China which is annoying.