Ratchet might have well hit him, with the force that Rodimus recoils. Or at least attempts to - it's hard to try and get away from the medic who's working on you. His relationship with Ratchet is already strained thanks to the vote, and if there's anything he doesn't want to hear from the other it's everything regarding that event and everything surrounding it.

Someone who isn't Rodimus would just sit there and take it, but Rodimus has had enough. He's nearly died, he's been yelled at by Megatron of all people, he's found out multiple who are dead have come back to life somehow and the last thing he needs, the very last thing he needs is this. So Rodimus glowers back at Ratchet, ignoring the warning signs that this an argument he doesn't want to have.

"You don't know anything about that!" How dare he assume that he does? Does Ratchet even know what Rodimus tried to do - come clean, only for Drift to tell him not to. It had hurt, it still hurt, that he couldn't stop his best friend from taking the fall. "You've made your opinion on my choices clear, Ratchet. I don't need to hear this from you."

It's probably not a wise idea to bring that up at this point, but Rodimus isn't gifted with a lot of common sense.