Gruff controllers are just a part of flying life, and it's better for the
student to learn that hearing someone else get it than him. Every so often a
guy gets his coffee seriously ****ed in, and the Nth pilot who gets his goat
is going to catch some heat. Sui generis, this case sounds like the pilot
over-reacting a little, and I agree that a "360 for spacing" call* prior
would have been a reasonable precaution. But, CFIs often get to know the
voices on the other end of the line pretty well, and their "personalities,"
and if I'd gotten the bum's rush from this guy once or twice before in a
similar case, I might have responded acridly as well.

In the spirit of self-criticism however, I'd also look a little more closely
at the CFI's acceptance of the original clearance. The difference between 11
and 2 o'clock seems well within the margin of error, more so if the two
cherokees were not on very different headings. I never acknowledge following
traffic unless I'm absolutely sure I've got the right one. I fly in very
busy airspace and goof-ups simply have too much potential for disaster. I've
seen one very near mid-air and been far too close for comfort (100') once
at my home field, both times right in the pattern at a Class D field with
radar repeaters and good controllers. FWIW I've heard lots of screwups on
the radio and never heard a controller chew a guy out quite that badly in an
area where authority was ambiguous.

* Controllers sometimes grumble when I announce that I'm doing something
when said announcement is not required, but my policy is that so long as
they have the right to file a deviation on me, then they are going to have
to live with my precautions. This is not to say that I always do it, but I
do it when my gut says so. For instance, I typically announce crossing a
runway when taxiing, but not at my home field, where I have a good feel for
the flow of things.