Well, (func blah blah blah) is doing a nice job of spinning, but as usual with spinners (including Assange) he's omitting context and details and applying different standards on the fly.
First, there absolutely was evidence of RPGs, and no-one (not even func-dude or Assange) disputes that the group of men were carrying AK-47 or AK-M rifles. It's true that the video does not provide _conclusive_ evidence (but there is evidence), but the soldiers flying the helicopters were also equipped with things called "eyes" and had a better view than a standard def video gives. [Nevertheless, two RPGs were found at the scene.]
Second, there was an actual firefight going on a few blocks from the scene (which is why the helicopters were there). Putting those together, we have a group of men carrying weapons moving in a combat zone. There is no rational viewpoint that suggests that the men were not a legitimate target. (Sure, you can argue that the coalition forces shouldn't have been in the country at all, but given that they were, armed men out of uniform moving around an actual battle are targets). Yes, it's really unfortunate that two of the men were not fighters, but it's equally unfortunate that insurgents killed western journalists embedded with US troops (such as Briton James Brolan).
Third, the second attack (on the van/people carrier) is less clear-cut. The conclusion reached by the helicopter crews (that the van was picking up the weapons and injured fighters) is not wholly unreasonable (people driving around during a fire-fight are not unlikely to be somehow involved in the battle), but there is a good argument that picking up wounded fighters is not a belligerent act, and therefore they should have let the van go. But this is second-guessing people who were in the middle of combat, so I'm not sure there's a "good" answer to this.
Overall, I'd say Wikileaks is a publisher, and Assange is (sometimes) a journalist, but you could say the same for the Daily Mail and Paul Dacre. And there's no question that the Mail/Dacre engaged in shady practices that should have been prosecuted, but weren't because of the difficulty in obtaining evidence. If that evidence existed (as it allegedly does with respect to Assange), then prosecution should proceed, in no small part because they _are_ publishers/journalists: they already have the power to spin the story however they like (e.g. naming the video "collateral murders", highlighting cameras but not weapons, excluding the existence of an active gun battle blocks away, etc), so they should _also_ be able to break the rules with impunity.
Oh, yeah: for those who like to try to discredit true statements with "citation needed": https://web.archive.org/web/20131020142823/https://www2.centcom.mil/sites/foia/rr/CENTCOM%20Regulation%20CCR%2025210/Death%20of%20Reuters%20Journalists/6--2nd%20Brigade%20Combat%20Team%2015-6%20Investigation.pdf