I always try to reverse a situation to see if it makes sense, and then I ask myself: what would we think if aliens came to earth to experiment on us with untested medicine, kill us afterwards and only when it is perfectly safe on us they would apply it to themselves. I believe a large fraction of humanity would say that that is unethical and they'd have all kinds of cognitive dissonance to deal with (and associated reasons why this is different) to explain why what we do is ok.

I personally don't think it is ok, but it apparently is a necessity, at the same time if this can be stopped then that would be great.