I'm going to agree with @anxietymaven here.
The flaw with your analogy is that those being voted down are not three year olds. They are grown ups with computers. And at this point, we should not be in the business of teaching a grown-up, "Hey, it really isn't polite to threaten violence or downgrade someone based on their gender."
But with your analogy, the community would have to constantly keep doing that, while the victim harassment has to keep putting up with it.
A one time mistake is understandable. Consistently daily harassment should be stopped. If it isn't, Steemit will always be niche.
It doesn't matter whether they are three year olds or 300 year olds. Conditioning of the human mind works the same at any age, only more repetition may be required the older they get. And yes, we should absolutely be teaching grown ups that it isn't polite to threaten or denegrade people. How else do you think they'll learn? And, if they don't learn, who do you think pays for that?
Finally, I agree totally that it needs to be stopped. I think I just demonstrated conclusively though that my approach is more likely have to stop it while your's is more likely to aggravate it. Simply downvote every vile statement while upvoting the contructive ones and the problem will solve itself over time. By contrast, downvote everything good or bad and you'll create a demon.