Yes, if there's one thing all the lies told about him haven't taught Harry it's to not believe everything he hears about other people.

I totally third this - you'd think he'd have cottoned on, after seeing Snape's POV about his dad, and the whole Pettigrew thing, and the whole ScarletWoman!Hermione thing, AND the whole Harry-is-off-his-trolley thing...wait.

Just shoot the poor kid already, there's no hope.