There is no question that they intentionally shot down that plane. It is simply inconceivable that they accidentally fired a rocket and it just happened to hit a plane. That plane was shot down because they wanted that plane to be shot down.
Let me play devil's advocate and say: Perhaps not.
Have we not had; in our OWN country; incidences of OUR military tracking and locking onto OUR civilian planes?
Practice - training what ever was the cause, the reports said.
If, just if, someone had ACCIDENTLY hit the fire button - those planes would have dropped just like the Malayian one.