There's a long and unfortunate story behind this one, First Aid. Though perhaps he'd always have been a sadist. Nature versus nurture is such an interesting discussion.

Proud? The First Aid is proud of him? And he's not even lying! He can tell when people are lying. It makes him feel... awkward, and he hunkers down closer to the ground, drawing his legs in towards Hus body. What is with this Autobot?

"I'm not doing it for you," he snaps defensively, then stares blankly at the question. "...Awhile."

Come to think of it, he probably hasn't done more than the occasional shake off and wipe down since he arrived. Cleanliness was never really one of his priorities.