So really there is no proof. Simple as that. It's finding guilt by proxy and heresay and tenuous supposition. Where there is no actual evidence of it. Anyone can claim that they slept with someone. Whether it be consenting groupies or whoever. Anyone could turn around and say I slept with somebody consensually at the age of 15, 14, 13 whatever. Somebody could say that about any person - anyone on this board, for instance. Anyone. My point is, you said "sexual practices with young girls" (not one girl, but girls) that has been "documented plenty of times." There's just no proof of that, as no other "young girl" or "girls" - not one- has ever come forward. Even now, two years after his death.
Bowie was certainly sexually promiscious in the 60's, 70's and 80's- including men. As where lots of rock stars and groups (indeed going back to the 50s). Like you said, it was different times. But there is just no real evidence whatsoever that he had "sexual practices" with "young girls". To me anyway. That's just my take. Though he most certainly bedded some of the most beautiful and famous women of his era - and even Mick Jagger! Oh, to be a fly on that wall!