I don't know what the official word on this is, but from my point of view Magnussen is equally responsible and Bergmeister could easily argue that he was just trying to recover from an overly aggressive bump and maintain his lead (It would likely be a lie, but he could argue it). I'd also like an angle from the front because it doesn't look like Bergmesiter is even touching him when the actual accident happens, but there is too much dust/smoke to tell. All I know is the last clear image shows about six inches or more between the cars and then Magnussen spins out in front of Bergmesiter.
Magnussen had already been penalized (had to give up his lead) in an earlier lap for an illegal pass and he was obviously willing to really push it.
It is clearly controversial, but this isn't the first time officials turned a blind eye to some questionable behavior. Last time though Bergmeister was the one that got shafted. And that may just be why nothing is being done here.