Seems like a reasonable decision, and good of the FIA stewards to explain it so thoroughly. Reading this thread and others on Autosport etc. a lot of people are obviously very emotional about the day so hopefully that statement will help to see through the red mist.
The statement appears to quite clearly to me say that Hamilton had himself alongside Rosberg before he went off track, at that point Rosberg can't just close the gap, I can't see how this isn't deemed entirely Rosberg's fault.
We see many many times a driver defend, he has every right to do so and to close off one side but the attacking driver has every right to continue heading down that side. If the driver behind gets alongside the driver ahead loses the right to not leave a gap. Rosberg had Hamilton alongside him and shoved him off the track.
Schumi vs Barrichello, Schumi went right, Barrichello went right, Barrichello still beat Schumi as he stayed right and got alongside Schumi before he could close off that side completely. AS a result even Schumi left space though it was mere inches of space against a wall. Despite not even putting him into the wall Schumi got a penalty for dangerous driving.
The simple fact is that you can defend however you like right up till the point someone is alongside. If someone is alongside you have to leave space. If this wasn't two Merc drivers, if this was any two teams drivers Rosberg would have a penalty for doing what he did. I really dislike that if an incident involves drivers from the same team and the team isn't pushing for a penalty things either get away without penalty or even not investigated. Rules are rules, teams shouldn't get away with breaking them because it only costs their own team.
Honestly there are so so many incidents over the years where a driver got alongside despite the driver ahead attempting to close off the gap and every single one I can think of either the driver who was ahead left room or they caused a collision and picked up a penalty, I see zero difference here.
Was it Magnussen got a penalty for pushing ALonso off in Spa iirc. The instant Hamilton gets alongside while on track the lead driver loses the 'high ground' and the choice to not leave space.
https://www.youtube.com/watch?v=v-FQ_uLqfGw
This got Magnussen a penalty, because Alonso went up the outside, Magnussen attempted to move over, ALonso got alongside before he could and Magnussen pushed him further AFTER Alonso got a bit alongside him. Even here ALonso wasn't forced 4 wheels off the track, he didn't lose control of the car because he was off the track. But this was a semi harsh penalty where Rosberg does something significantly worse, more dangerous and caused the end of another drivers race and it's no penalty at all?