From the video it looks like he was about a foot away from the wall, so a longer pitwall probably wouldn't have meant he touched. And even if he had, he'd probably get a puncture or a bit of steering misalignment. And even if he'd touch MSC's car, it's doubtful the car would have taken off - that's still fairly rare in a single seater.
To suggest that it was millimeters away from the death of one or more drivers, or spectators, is just silly conjecture founded on nothing.
Was MSC beyond the line of acceptability? Yes, a bit. His punishment seems right to me. He moved once. He moved back when Rubens needed room. It was a hard move, but it was only just beyond the realms of acceptability.
This isn't an arrive-and-drive karting meet for 9 year olds, this is the allegedly premiere series, where the best drivers in the best cars are competing. It shouldn't be easy. Drama is what we want. Risk is an unavoidable part of that - indeed, most 'fans' probably watch hoping to see a crash of some sort.
All the drivers in F1 have done similar moves in their career - Webber, Vettel, Rubens, Jenson, Hamilton, Alonso, Massa, Schumacher, Hakkinen, Coulthard......