Even his contemporaries thought that his behavior was exceptional and worthy of comment, though. It's less that such behavior was accepted in his time than that it was tolerated of a "great man".
It's important to understand that his attitude and behaviour were common at the time, but also that the means of condemning it and punishing it were much more hidden then (and invisible to us today): whisper networks among women to keep their distance because he was "handsy"; his male friends telling him that he should be careful because one day an angry husband or boyfriend might punch him out for his behaviour. It was handled quietly and informally, and with very limited effectiveness. Mad Men didn't get into this side of it.
Low status men might notice they don't get invitations to dinner that other men get, but high status was effectively immunity: Asimov was important; you couldn't not invite him to a con or a party.
I find myself angered by the negative reactions to my comments here. Are people seriously suggesting that Asimov's attitude was unusual for the time? Actions, perhaps, but attitude?
I will defend my comments! Men of that era, in that society, were incredibly sexist. Women suffered through that, and continue to suffer today.
If people here can only react emotionally without comprehending what they're actually reading, there's not much hope to improve anything.
OK, I'll clarify. His attitude was a product of the time. I love that his fiction had strong female protagonists, but his everyday attitude toward women is typical of the era.
Mad Men illustrated this very well (slight spoiler: especially consider what happened to Peggy, by Pete, early in the series..). Women were expected to take a lot 'on the chin'. After all, guys will be guys, right?
If others raised eyebrows about his behavior, it was only because it was more risqué than normal, but not out of any consideration for the victims.
His female protagonists were mostly sex objects. The only exceptions I can think of are Susan Calvin (who is portrayed as hardly a woman at all) and Arkady (too young, just).
Normal not, but widespread and tolerated by society at large yes. Pinching, grabbing, hugging, making lascivious comments and cat calling had the same treatment as swearing, it was considered rude, but nothing more than that...