There are no verses about burning their bodies, only to kill. Is it the burning part that you wanted clarification on?
The Sahi Hadiths are full of verses exhorting you to kill people for apostasy, which includes abandoning Islam or one of the core tenets of Islam. Rejecting the prophethood of Mister Mohammed, or even his finality, falls under that banner. So yes, anybody who criticizes Mohammed is a blashpemer who ought to be killed. Blasphemy is an act of apostasy under Islamic jurisprudence.
"No doubt, I would have killed them, for the Prophet said, 'If somebody (a Muslim) discards his religion, kill him.'":
(
Sahih al-Bukhari,
4:52:260Sahih al-Bukhari,
9:84:57Sahih al-Bukhari,
9:89:271Sahih al-Bukhari,
9:84:58Sahih al-Bukhari,
9:84:64)
The story goes on about how Mohammad sanctioned his disciple to use treachery to kill someone who had hurt Allah's apostle. Yes, this is also from the Hadith (Bukhari,
Volume 5, Book 59, Number 369)
Yes, killing people for insulting the prophet or even denying his prophethood is well and truly part of the religion of peace.