You're right about no yellow flags though. Thats just stupidity!

However, he takes NO avoiding action, and hes looking straight ahead at the time. Doesn't even try to jink out of the way, and its not that blind a corner.

If he cant see marshalls on a track, when everyone around him manages to, he not fit to race. Simple.

Racers ought to know, that these marshalls dedicate their time so people can go racing. And the safety of these people is paramount. Accidents happen of course, but this was completely forseeable and avoidable.