And what 'character assassination' would that be?
Bernadotte was an enemy of his superiors and his actions in 1806 and 1809 brought disgrace to himself.
Marmont's treasonous actions in 1814 were dishonorable and were negatively viewed by Ney, Caulaincourt, and other senior French officers.
That isn't 'character assassination' it's an assessment of the facts.
There are frequent apologists for both Bernadotte and Marmont, and what they did or failed to do (the same can be said about Dupont) and I have found that those who continually offer apologies or reasons why their actions are acceptable usually are anti-Napoleon.