I think there's a definite grey area where the driver being overtaken doesn't leave enough room, and the overtaker has to go off-track to avoid a collision.
You need some co-operation to overtake around the outside, and in the 'old days' (before the tarmac run-offs) you would normally get that, otherwise there would be a crash.
I had another look at the incident to check that Ricciardo wasn't forced off by Sutil, but it's very clear in this case, Sutil lifted or braked and allowed Ricciardo to overtake, so Ric could actually have turned in slightly earlier than he did. Probably he wasn't expecting Sutil to concede the corner quite so easily.
A definite penalty. Did anyone interview Ric or was he getting angry in private?
I agree it‘s often hard to tell, when a driver fails to make an outside-line pass within the track limits, whether that‘s because the defending driver is more prepared to force his rival onto the run-off than he would have been, in previous years, to force his rival onto the grass or gravel knowing there would be a massive accident. But you have to remember that, when there were no tarmac run-offs, some of the "brave" outside-line passing attempts we now see wouldn‘t have been attempted at all. If you want to blame the other car for the fact that you went off, it has to be clear that the other guy ran you wide and failed to give you the space demanded by accepted racing etiquette. In my vieew the benefit of any doubt should go to the car that stays on the track.
In this case I really don‘t think it‘s possible to make the case the case that Sutil was to blame for Ricciardo going off.