I may be a bit late to poke my nose into this discussion, but in my opinion ATC operators are as well trained at their job as pilots are in theirs. Therefore, also in my opinion, this sort of un-professional behaviour on the part of ATC amounts to the equivalent of pilot error & I believe should be treated as such. ATC are there to assist the pilot to maintain safety, not the other way round. There seems to be an attititude here that ATC are God & cannot be held to account unless someone dies as a result. If the pilot of the "faster" a/c had declared an emergency, fine, if not then he should do the maneuvering as he sees fit. In my opinion. And I think it is bad news that ATC controllers are doing things like this which they would not have done a few years ago, ie: being less than professional.
I would point out by the way that this is only my opinion.
I shall now take cover.