Danobee is right: You ran out of air (or got way low), you've proven you don't know what you are
doing. So the donor is the boss.
There are several reasons why someone could be low/out of air that have nothing to do with whether they know what they are doing or not. The term is "Failure."
I don't think you can assume that someone is out of control simply based on them being low on air. If they had a problem and they managed it with out panicking that lends more credibility IMO that they do know what they are doing.
People on both sides can cite issues to bolster their view point, but generalities like this can be counter productive.
OTOH, if the diver appears panicky the donor needs to take whatever steps are necessary to control the situation safely.