What in the koran, or in Muhammad's pbuh life, instructs Muslims that Islamism is wrong?
I doubt that anyone can cite anything.
I doubt this because if there was something, then many so called moderate muslims would have cited it, and famous Islamic lesbian reformer, Irshad Manji, would not have argued that the remedy for islamism is a figurative reading of the koran and sura and hadiths. (This argument tacitly admits that what justifies islamism and islamoterror are the explicit words, sentences, and edicts in these essential islamic texts.)
NOTE ABOUT DR. CARSON'S POSITION THAT HE WOULD NOT VOTE FOR A MUSLIM TO BE POTUS: though many muslims do not behave in any way that is antithetical to our founding documents and principles, their holy texts do demand behavior that is antithetical to our founding documenrs and principles.
The holy texts of Judeo-Christian religions are not antithetical to our culture or our founding principles; in fact, they are its foundation. And none compel non-believers to believe or to behave in any way, let alone in any way that is antithetical to our nation's values and principles.
Compulsion is the exclusive domain of islam, and it's a principle reason why it is incompatible with the West.