I would expect regardless of how good the source was, first exposure, assuming the recipient considered it a valid source, would tend to be believed at that point and make counter exposures more difficult to believe.
My first exposure would have included the "saving American/Allied lives version" though I do remember thinking "why was the second bomb necessary, why so soon after the second, and was it not in part revenge?".
But that version, "saving more lives" isn't set aside in my mind by knowing Emperor Hirohito was in favour of, or considering, capitulation prior. It's just sad to think that the bombs were used, regardless if they were better used that not. I find it extremely hard drawing lines with regard to civilians and war in most cases. Sometimes it's easier than others. Sometimes I agree with what, say, the UN or international community might find acceptable and sometimes I find it bizarre.