Riel was committed to a mental asylum in Longue Point in 1876, then to the Beauport Asylum near Quebec City.  Modern biographers have speculated that he may have suffered from megalomania.  "Madman" may be a harsh term; "mentally ill" would be more accurate, although I doubt Mr. Cardinal would include this in his narrative instead.

Riel also had a prisoner, Thomas Scott, executed.  Would this be in Mr. Cardinal's narrative?

Riel was a polarizing figure.  If Mr. Cardinal's point was that the portrayal of just one pole was problematic, then he has a good point.  If his point was that one pole should be replaced by the opposite indigenous-friendly version, then that's a problem in itself.