I think the penalty was totally deserved. Not just because of what was done but where it was done - at a fast corner that all drivers seem to agree needs rethinking.
Would anyone support a driver that did something similar in the middle of Raidillon?
I also have to agree with garoidb's assessment of the stewards' judgement.
How was Alonso's action not the cause of Russell's accident?
Were they of the opinion that Russell was going to crash even if Alonso had taken the corner as he usually had?
Russell definitely has some responsibilities, but...
Bizarre!
The problem with the ruling is that the stewards said, specifically, that Alonso was not responsible for "the dirty air that caused the accident". Maybe they got that wrong, but by getting that wrong they also got the ruling wrong. I think most of us can agree that if Russel had not crashed, Alonso would also not have gotten a penalty.