By Obi Wan's twisted mental gymnastics and logic, Anakin had already died by then and had already become Vader, by the time he said the jedi were evil.

The younglings were young enough that the jedi hadn't brainwashed them to enough of an extent. They were still blank canvases that could be painted any color; indeed, they were not even jedi yet.
But that ol' hothead Anakin was always more into negotiations of the aggressive variety