Playing devils advocate:
It's the logical conclusion based on what we know: - You mean not very much?
A senior rebel boasted on social media about shooting down a plane and deleted those messages when it became clear that it was a civilian airliner. - In all fairness that is standard procedure for rebels anywhere in the world, see a plane come down, assume credit. In fact IIRC didn't the Iraqi army try to claim an F15 that suffered mechanical failure? Anyway the point is that if they saw what looked like an An26 come down they would obviously claim the kill, plus the profile on VK (Russian Facebook) isn't even run by Strelkov himself so anybody could have posted that.
Radio intercepts of rebel communications discussing the shoot down were released by the Ukrainian government soon after the crash. - Well a conversation between two unknown parties can't possibly be faked, im sold
The rebels have impeded access to the crash site. - Crash investigators have actually been quite complementary of the rebels efforts, despite what the media say. If by impeded you mean not just roll over and let everyone and everything into their territory during a civil war, then lol
A BUK missile launcher was moved across the border into Russia shortly after the attack. - All we have seen is pictures/video of a Buk, somewhere in time, that's hardly concrete evidence, and if it was the guilty one then the USA would have satellite footage of it the whole way including when it launched and when it entered Russia, but all their moaning about is social media evidence