was Hugh Heffner ever been publically accused or threatened with lawsuits for sexual harassment or misconduct by the the main stream media?

No, babygirl. Hef was part of the "main stream media" back in the day, and he did a lot to remove old censorship laws that actually allow you to see/hear/read what you do today - and I am not talking nude women. Hef is dead; if you want to talk about him, you need to understand who he was. Peace, sister.

His whole life was about multiple partners and it was very public. If a girl knowingly joined his group at the Mansion, how could she then claim she was sexually harassed?

To my knowledge, no. Not by the " main stream media" or anyone else. As far as I can recall, the closest run- in to the law he ever encountered ( other than fighting close minded bigots on the far right) was an incident with a guest using drugs at the Playboy mansion. Hefner was not personally accused, but afterwards he enforced a strict rules about illegal drugs being banned from the mansion.

No, he was probably gay and used his bunny girls as cover.