Re: Location non employee on business property
My first comment is: he sounds like a bona fide jerk.
Second: your remedies are limited. You can not sue for employment discrimination.
Third: this guy's behavior may be curbed if your brother's coworker is encouraged to file a claim with the EEOC (assuming she was harassed within the last 300 days). Or the DFEH (if over 300 days, but within 1 year).
As for whether your brother might have a claim for employment discrimination, this poses an interesting question, but these would be somewhat uncharted waters, legally speaking. To have a claim for sex harassment, the employee must be experiencing a "hostile work environment." So first, it depends on how severe or pervasive the harassment is. It is conceivable that, for example, a non-Jew could find a hostile work environment if his employer has a flag with a swastika on it... likewise, it is conceivable that a male might find a hostile work environment in the way women are treated. But this is, legally speaking, murky. It would not hurt for your brother to file a claim with the EEOC -- but then there is the possibility that he might be retailiated against.
But if he is retaliated against, now he is on somewhat firmer footing. It is illegal to retaliate against someone who complains about employment discrimination, even discrimination against another person. But murkiness arises again, in that your brother would be filing about discrimination against a non-employee. Protected under the laws? As far as I know, this question has not been decided.
I would suggest consulting an attorney (one with extensive background and expertise in employment discrimination), and/or getting your brother to visit the EEOC office which has jurisdiction over the place of employment (check their web site & call their 800 number for this info). You will be able to speak with an investigator. Request that the investigator consult with an attorney about these novel issues BEFORE filing a claim. You don't want to put your bro's job in jeopardy if he doesn't have a leg to stand on.
Ultimately, it does not appear that your case is very strong, just because the law is silent on so many of these issues. Best of luck to you.