It's easy to quarterback from a keyboard, because the unmanageable run-away ascent wasn't an existing condition to overcome, it was caused by the rescuer, it was a created condition due to using both BCDs instead of one.
This has been the point that the current while strong and angling slightly downward was not the mythical deadly down current that so many posters are now posting on scubaboard about, and asking if it's safe for them to dive in Cozumel because of these mystical downcurrents and incidents like this one recorded on video that appear to record how dangerous they are. The reality is this was self-induced, a too fast descent, bad habits such as the diver using only his legs and fins to stop his plumet, not adding air to his BC to get to neutral prior to feeling the pull of the current.
This video to me is the opposite of what many see it as, it's a good example of how manageable a Cozumel down current really is. If you follow your training and dive conservatively there should be nothing to worry about. As TSandM stated, more than one diver on this same dive was able to easily descent and rise and move about in the current. The video shows the fine line in diving how you can be either in total control of yourself and out of control. It's a great video for study.