The problem here is that Assange didn't kill any people, while Uncle Sam has killed hundreds of thousands for oil, revenge, and preserving the hegemony.
Arguing that he hasn't personally killed anyone is not a strong rebuke against such allegations.
The risk inherent to collaborationism is also not one anyone but the informant must account for. Just as mercenaries operate in that same high-risk-reward / low-solidarity space, and accordingly join the cast of characters in war zones along with spies and informants without international sympathy.