FWIW here's my read of the rules and where things went wrong. I have no dog in this fight btw.
19 ROOM TO PASS AN OBSTRUCTION
19.1 When Rule 19 Applies Rule 19 applies between boats at an obstruction except when it is also a mark the boats are required to leave on the same side. However, at a continuing obstruction, rule 19 always applies and rule 18 does not. 19.2 Giving Room at an Obstruction
a A right-of-way boat may choose to pass an obstruction on either side.
b When boats are overlapped, the outside boat shall give the inside boat room between her and the obstruction, unless she has been unable to do so from the time the overlap began.
c While boats are passing a continuing obstruction, if a boat that was clear astern and required to keep clear becomes overlapped between the other boat and the obstruction and, at the moment the overlap begins, there is not room for her to pass between them, she is not entitled to room under rule 19.2b. While the boats remain overlapped, she shall keep clear and rules 10 and 11 do not apply. <-- This part here indicates that Courageous had no rights to come from astern and expect to pass a continuing obstruction if there was no way she was going to make it through there when the overlap was established
20 ROOM TO TACK AT AN OBSTRUCTION
20.1 Hailing When approaching an obstruction, a boat may hail for room to tack and avoid a boat on the same tack. However, she shall not hail if
a she can avoid the obstruction safely without making a substantial course change,
b she is sailing below close-hauled, or
c the obstruction is a mark and a boat that is fetching it would be required to respond and change course.
a After a boat hails, she shall give the hailed boat time to respond.
b The hailed boat shall respond even if the hail breaks rule 20.1. <-- Even though Courageous's hail for room did not qualify under 20.1b (due to sailing below a close-hauled course), Extreme2 was still obligated to respond in the appropriate manner as written in 20.2c. Sorting out the legality of the hail should be left to the protest room.
c) The hailed boat shall respond either by tacking as soon as possible, or by immediately replying ‘You tack’ and then giving the hailing boat room to tack and avoid her.
d) When the hailed boat responds, the hailing boat shall tack as soon as possible.
e) From the time a boat hails until she has tacked and avoided the hailed boat, rule 18.2 does not apply between them.
As is often the case in life and sailboat racing, the reality is often somewhere in between both sides of a disagreement. Courageous seems to have been in the wrong due to violation of 19.1c but Extreme2 could be held accountable for not responding to Couragous's hail appropriately under 20.2b.