I was in the stands right in front of the wreck, magnussen should not have hit him in turn 11. But he should not have spun him at high speed like that.
There's an eleventeen-billiondy page thread in AutoX/RoadRacing about this. There's a lot more going on than just what happened in that incident, lots of history between them in the closing laps of the race.
Regardless I think it's inexcusable and I am shocked ALMS didn't take any action against him. Sure, there was contact in 11 but I'd argue the P-car lifted on turn exit trying to make the 'vette lift since he knew with a fair run off 11 the 'vette would walk him (if the P-car lifts, he's back on the throttle by the time the 'vette reacts/lifts and maybe even bumps him for a little extra run for the P-car and loss for the 'vette as was the case).