I think it all depends on the car. As Michael pointed out – if he is stuck fighting in the midfield he will no doubt have a tougher time than most dealing with ‘racing incidents’. If however the car is fast enough for him to be able fight for pole then I reckon the drivers around have too much to lose by being overly aggressive with him.
Based on this I suspect 2013 will be a woeful year as I sincerely doubt the car will be up to spec. 2014 could be a very different story. McLaren are apparently looking for a new engine supplier and this cant bode well for their 2014 season. So maybe this decision will pan out.
I also heard that he was an absolute nightmare to work with. Apparently he was exceptionally moody and hard on his mechanics. I suppose he couldn’t handle being mediocre. I think this was a large factor when they decided to let him go.