Yes, my tone is very hostile and critical, and it's not only my tone. I don't agree to be a bystander when you says such things in such a tone. You're tone is very critical, and is quite the opposite of "very calm, reasoned and measured".
According to the froum rules, you might have the right to say whatever you want, but according to society rules, you must not say such things in such a tone when it isn't your bussiness whatsoever.
It might be that the first rule of medicine is "do no harm", but if this rule was enforced - than there would be no medicine. Every drug has side effects and some risk. Some of them are more risky and some are less risky. It is therefore a judgment call. Anyway, Sue knows that it's risky, sue knows that it's toxic, Sue knows that she did not test positive for XMRV and Sue knows that it might cause her problems in the future (drug resistance, problems with testing and more). However, Sue chose not to wait for the science to be finished - because this might take a long time in which she have to live in suffer - and to try these medications. There is a rationale for these medications to work, and by the way, there is currently no other approved drug for ME/CFS, so trying "safer" ones might also make more harm than good (what would you prefer - take a safer drug that would not work and then the more dangerous drug, or take the more dangerous drug in the first place?). Besides, Sue have tried other "safer" drugs in the past. They did not work for her.
You said:
Afterwards you have talked about doctors, and perhaps you meant only the doctor - but the direct translation of what you said is that a person who takes antiretrovirals when doesn't know if he have XMRV is irresponsible. Besides, you called Sue "crazy" for doing that.
For the end: If medical standarts say it's irresponsible to give a patient in a desperate situation, whose days are not days and nights are not nights, some somewhat dangerous drugs, because these drugs seems to have the best chance of helping that patient, and the patinet undersatnds the dangerous and wants to take these drugs - than I hope there are many doctors out there who are considered by the medical standarts to be irresponsible.
Anyway, even if you think it's not wise, you should not say it like that. You can advise her to do what you think is best for her - but you should not do that in such an aggressive and repulsive way, because this is not your decision to make.