Instead, you'd do this by showing how Peterson's claim is unsupported by evidence, specifically on how his view pertains to the current topic.
He supported an alternative theory.
But he was already 50 years years old when he published his first essay on HIV, and over 60 when he started the campaign against HIV/AIDS correlation.
And most of his theories have been disproved by following studies, his first publication on the subject is date 1987, Montagnier discovered HIV in 1986 and it was taken for granted as a fact years later.
The best moments of Duesberg career had already gone (like 30 years before).
Montagnier himself late in his life, at the age of 77, gave a speech that basically supported the validity of homeopathy.
I bet it's more an aging related problem than a credibility problem.
BTW Duesberg was wrong on HIV but not on the other topics he studied.
I have no reason of doubting your warnings on Peterson, but it may be possible, as in the Duesberg and Montagnier cases that he might be wrong on something and right on something else.