No its not. If you ever work in big companies you will know that.
> Adults shouldn't have their employer telling them that sexual harassment is a no no.
Yes they do,
Assuming you are a male, you might be unknowingly harrasing female employees just by having a boys will be boys attitude. So an employer has to give you training and explain you why its wrong.
Some people use throwaway accounts to harass other employees on social media, if your employer gave you the training you would have learnt that is wrong.
> The policy is the law.
Exactly, now you get it, the company may get into legal trouble if they dont have an official policy or they make it super difficult to report complaints.
> The responsible thing is to involve the authorities when one of your employees is committing a crime. Simple as that.
No its not simple as that, just telling the victim to go to authorities is just washing your hands, a responsible company also makes sure that victims can file a complaint with the management. Not all victims want to file a police complaint, that does not mean they the abuser should get away with harassment. The company should still investigate and fire the abuser and then file a complaint with the victim's permission.
These are some of the aspects which you will understand if you been through some training.