Thats after his life (Padme and his unborn child[s]) are stripped away from him. He hates that part of his life after ROTS and wants to forget that he was ever Anakin Skywalker. It torments him. But in ROTS he's not fully evil, or fully Darth Vader yet thats why he responds to Anakin. He doesn't hate himself (Anakin) at this point. When she dies, he does.
Re: Anakin or vader?
Originally posted by steverules
Why did Vader still reply to the name Anakin when Padme and Obi wan tried to reason with him?
Since although he at the time went by vader he still lived basicly his whole life before that going by anakin and was still very aware that some peaple refer to him as anakin still.