I think that's nonsense - Nicholson wasn't even there at the time. Polanski had taken photo's of the 13 year old girl before (so was well aware of her age) before he invited her for the private photo session where he drugged and raped her. He admitted having sex with her (including knowing she was well underage) - his only partial defence was that ti was consensual (denied by his victim), however that wasn't much of an argument given he knew she was 13.
There are quite a number of additional allegations coming out about Polanski as well, including some that are similar to Weinstein as well as others which also involve underage girls. From what is currently available in the public domain we can see that Weinstein is bad, but Polanski appears much worse given the age of his admitted and alleged victims.
Only you are quoting the mythology of Hollywood against that claimed by others who were actually there and the other actor was Peter Fonda. Polanski had made Rosemary's baby and had done so with the aid of the California "Satanist" community amongst others, they appear in the apartment scene at the end. The film studio re-edited the film without Polanski's knowledge or permission however, Polanski took the rap for it from the Satanist community and it is often said he was running scared for several years of their "revenge". His film "The Ninth Gate" is often seen as his "apology" to that community.
That's in no way to deny he had dodgy tastes however, I would imagine something such as his version of Tess of the Durberville's would be a far more fruitful grounds for allegations of abuse, given the now known history of its' star Natasha Kinski and the dreadful childhood it is claimed she suffered.
At the same time Polanski was meant to have committed his crimes, a friend of mine who later killed herself, was being systematically abused by half the men folk of the village she grew up in in "nice and safe" South Yorkshire. When she "ran away" to a "big town" and reported said abuse, she was returned to her home and absolutely nothing was done to investigate her claims. Just maybe, had some film producer abused her, people might have been far more inclined to listen to her claims simply because it confirms a prejudice about "showbiz people".
Furthermore, I recently discovered to my horror that, another friend who killed herself, was systematically abused by her father only he was a "right honorable", so nothing was done there either. The point being, the whole Hollywood thing is as ever, being used to berate Hollywood by much of the media rather than, address the awful reality of life in the USA and the UK in 50s.60s.70s.80s where, the abuse of children was endemic to society and we did less than nothing in fact, we made it worse by making it virtually impossible for victims to come forward.
There was a period in the 1970s where in Hollywood, mothers would aggressively "pimp" and there can be on other word for it, their daughters to the film industry and music industry using fake IDs to obtain entrance to any number of venues and parties they would not have otherwise been allowed anywhere near. Ergo, when you hear of stories from the 70s involving so called "kids" and Hollywood, one needs to be circumspect and then some about the veracity of the claims. These were almost wholly "kids" who would scare most 50 year old blokes and make them feel about as worldly as a vicar from some sleepy English hamlet in the 1940s. There's an interview with Pamela De Barres about what went on back then and she pulls no punches at all about how, her position in the hierarchy was usurped by girls in their teens who were almost all under the aegis of their mothers.
Funnily enough, one of the most powerful ex pats in Hollywood is an old mucka of mine from the days at the Speak. She makes no bones that one of her key promotions came after she , as everyone knew she would, drank some exec under the table in less than 2 hours and he immediately promoted her on the understanding that his "failure" was not made public. He thought he was going to get a "leg over", he ended up bent over the loo of an infamous nightclub talking to god on the great white telephone for about 3 hours. Ergo, to try and extrapolate Hollywood and showbiz to the rest of the world as some sort of overall dynamic, is both intellectually dishonest and ridiculous.
I truly hope that, the Weinstein revelations are the watershed for sexual abuse and that, those of both sexes who were intimidated, conned, and outright forced into sexual relations with people who held positions of authority feel they can say "me too" and that we as a society , can actually address the whole problem finally, in something resembling an adult manner.