He's responsible for it in a way, but... not entirely. It was sort of accidental- it pulled and pieces of his personality usually repressed.
Like- the child soldiers in Africa kill their families... but they're drugged, they don't know what they're doing really, and the drugs have warped their minds to an insane degree.
All the drugs did was make him paranoid... xenophobic. He had the talent from the OO that made it worse. It doesn't mean he secretly wanted to kill everyone, though he was always clear with Sisko that at a choice between his life and others- he'd pick himself.
I don't think he'd be punished today, let alone then. Today, he'd be released once his mental problems were solved.