He's hiding out from a regime that has demonstrated a willingness to torture him and violates the Geneva convention and other international law with impunity. I'm not sure where you have gotten the idea that he is a coward. Clearly, he is braver than me, you, or most of the other posters in this thread.
I don't see what he has done that was brave. Manning, Snowdon etc. are genuine brave people acting selflessly to try and make a change. Assange is a politician first and foremost looking after his own image and self before anything else. Plenty of people who knew/know him will attest to this.
