This is silly whataboutism. They have plenty of evidence, including PST/PDT timestamps and proof he logged out of other personal accounts when he logged into that account, that suggested it was him. Despite his claims, they watched him extensively and found no indication that anyone else was posing as DPR.
Not to mention that he was caught in part because the first public advertisements for Silk Road were traced back to his personal accounts, and there's strong evidence that he personally grew the first batch of shrooms that launched the market. It was all him from the beginning.