They were expecting military plane, they were told THIS plane is military plane and they shot it down. And after that, they were very surprised to find sea of bodies, not military equipment.
If you have a equipment to down planes, it's also your duty to have the proper radar equipment to reliably see what's up there, something that those Rebels did not have. They just stole equipment out of their league, did not know how to handle it and killed 300 innocent travelers.
This is right. It has been pointed out that both the Ukrainian government and the rebels now have the capability to do this, the Ukrainian government has had it for a long time, without incident. Because under a government it is operated by soldiers who follow procedures and have access to the data about known civilian flights.
It gets a bit worse than that I believe, officially to this date the blame is still on Iran for flying an airliner according to it's flight plan and in the commercial traffic corridor.
They shot down a A300 thinking it was an F14, and they were in a heightened level of alert because they (the USS Vincennes) were in Iranian waters, chasing a small naval boat that they claimed shot at their helicopter.
As an aside, the IR655 tragedy was one of the first were data was available to separate fact from fiction.
Indeed. Heck, even someone with FlightRadar24 (an app the price of a cup of coffee) could probably deduct what plane that was. Let alone if you have advanced equipment.
As you say, they just got their hands on equipment and had little clue how to handle it. They are also fully responsible for what happened.
They stole a machine designed to kill others, and then used it in a reckless fashion. They are responsible, and can't use the "but my friend said" defence, I'm afraid.
If you plan to use such weaponry you have a duty to confirm whatever it is your are shooting at is the right thing. Especially if it is a known flight path for commercial airliners.
I agree with you that they likely didn't intend to shoot down a commercial, rather than military, plane but that doesn't absolve them of responsibility.