We know Russia has been supplying the rebels with heavy weapons. It's unlikely that Ukrainian pro-Kiev "neo nazis" marched a heavy SAM launcher through rebel controlled territory. Also, in any case, it doesn't follow that because someone is a "neo nazi" they will shoot down aircraft.
> We know Russia has been supplying the rebels with heavy weapons.
More than that, we know the rebels themselves claim to have captured exactly the sort of weapon that would be able to do this (Buk missiles) from a raid on a Ukrainian military base.
>“The plane was shot down by the Ukrainian side,” said Serhiy Kavtaradze, a member of the rebels’ security council, according to the Russia’s Interfax news agency. “We simply do not have such air defense systems.” He said rebels’ shoulder-launched antiaircraft missiles “have a firing range of only 3,000 to 4,000 meters” and that passenger jets fly at much higher altitudes.
...
He denied that the rebels possess the SA-17 Buk air-defense as Kiev alleges."
The stories in which the Donetsk People's Republic -- the initial claim that they had the missiles didn't come from Kiev, though the claim that they had used them to shoot down this plane did -- claimed to have captured the Buk missiles [0] were before this incident (and they've apparently shot down Ukrainian military aircraft recently beyond any altitude that MANPAD missiles would reach), so the furious backpedal and claiming they don't have the technology now is somewhat dubious.
It could, though, be an honest retreat from a propaganda misrepresentation that has since become more of a burden than a benefit.
(Incidentally, I upvoted the parent because even though the claim may be dubious, noting the fact that the claim has been made is a valuable addition to the conversation, IMO.)
More than that, we know the rebels themselves claim to have captured exactly the sort of weapon that would be able to do this (Buk missiles) from a raid on a Ukrainian military base.