After reading all of the posts I've come to form some thoughts about the situation.

Regarding when does the slide begin - given that a legal slide feet first, according to 2-32-1 requires at least one leg and one buttock in contact with the ground. Logic says that the slide actually would begin on a head first as soon as at least one arm and part of the torso contacted the ground.

Since this is not the case, what we have is a runner diving into a catcher who has the ball and is attempting to make a play. From this you have several issues.

* This is not a slide, but a dive.
* It became a dive when contact was established with F2 while still being airborne.
* The runner does not attempt to avoid contact with the catcher.
* The runner turns a shoulder into the catcher, also showing no intent to actually "slide"

As soon as the runner turned a shoulder, it went from intent to slide into intent to knock ball from F2's position.

Depending on how you want to interpret slide/non-slide, you have to invoke either 8-4-2b or 8-4-2c, with 8-4-2b carrying the automatic interference. In either case the runner is out.

Regarding MC, based on the thread, one could logically think MC occurred. It's still an individual judgment, and I would probably rule that way. It's still one of those HTBT to give a definitive ruling. Obviously PU did not think so immediately but much after the fact, and only after confrontation with the coach, although I don't agree wioth changing the call for that reason. You either call it or you don't, but not because the coach decides to get in you face. Kind of like punishing a kid for stealing a cookie from the cookie jar an hour after the fact.