I have now seen the video, too. Yes, it was an ugly pass, and I wouldn't be pleased if someone did that to me, either.
But. I would love to see this from the other rider's perspective. I've BEEN that rider who did an ugly pass like that. I had no intention of doing so, and I highly doubt that this rider intended it either, but that's how it went down.
Keep the following in mind:
The camera bike had just done a high 1:57. The rider in question did something like 1:41 on Sunday and although it's possible that he would have not been quite at that pace a couple days earlier, it likely wouldn't have been too far off. (By the way I love the on-screen track map and lap timer; I'm not that sophisticated)
The camera bike has about 120 - 130 horsepower. The R3 has about 40. We all know that. There's an obvious difference in straightaway speed and acceleration in favor of the camera bike. But with the R3 doing 16 seconds a lap faster ... that rider has an obvious cornering speed difference.
The camera bike had completed several corners in which the bike was several feet off the inside edge of the corner leaving a ton of room on the inside. The camera bike had just gone into the entrance of 4 well towards the outside edge of the corner (read: upcoming rider can not pass on the outside, no room to go there) and had then disappeared over the edge of the hill from the point of view of the R3 rider who is approaching fast with a much bigger difference in cornering speed. From that rider's point of view, since they cannot see what is actually happening in corner 4 itself, they can only predict what the rider in front is going to do by what they've seen in the seconds leading up to this and perhaps the previous few corners in which the bike in question was in view.
Now the R3 rider comes over the crest, has now committed their entrance speed and approximate cornering line ... and they are now coming up fast on a space that is quickly disappearing. At that point that rider would have had no choice but to aim for the remaining gap and hope for the best. Slamming on the brake while at full lean is not going to work out well and the resulting crash could easily take out both riders. Changing direction to go around the other side ... it's too late for that.
It was probably an error on the part of track day organizers to put anyone with a race license in the green group. It was probably also an error to not, somehow, accommodate a request to change groups.
Mosport is not a good track to learn how to function on a race track ... especially the days leading up to the national. The days leading up to VRRA may have been a better choice.
My own opinion is that nobody should do a track day until they've done a school; I have no idea if that applies to those involved in this situation or not. My own opinion is also that nobody should go in red group unless they either have a race license, or have had one in the past, or are known to the organizers as competent and fast riders.
At track day riders meetings it's often said that if someone is holding you up and you can't pass them, pull off the track and rejoin. Problem is, if you have a bike that is doing (let's say) similar lap times but in a very different style from the usual 600cc/1000cc modern sport bikes, it doesn't work. If you pull off and rejoin, the same thing happens with the next bunch of riders that you come up on. It's impossible to have a clean lap.
I stopped doing track days because of the somewhat similar scare that someone gave me ... and that was because of a slower rider in red group who (IMO) should not have been there.
VRRA has addressed this for their (large) practice groups. Everyone is assigned a practice group depending on category of bike (addresses the "difference in style" the best we can) and lap time based on that rider's known lap times. Only riders new to the organization with no lap time history whatsoever have to take a guess at it, and only for long enough until that rider's lap time becomes known ... then they get assigned. If the same logic had been applied here, pretending that these two bikes were Period 3 or 4 vintage bikes, the camera bike would have been in "slow" (1:48.10 and up) and the R3 would have been right on the cusp of being either "medium" (1:42.60 to 1:48.00) or "fast" (below 1:42.50). I'm right on that cusp, too, having done 1:42.6something.
There are still differences in cornering speed within each group but they're not so large, so you don't tend to have situations of coming up on someone enormously fast mid-corner.