This is not true and it does not look good for him to say it:

The legal and social understanding of sexual harassment, however, varies by culture.

In the context of US employment, the harasser can be the victim's supervisor, a supervisor in another area, a co-worker, or someone who is not an employee of the employer, such as a client or customer, and harassers or victims can be of any gender.

https://en.m.wikipedia.org/wiki/Sexual_harassment

But, I do generally agree that two wrongs don't make a right. I am pretty appalled to hear that he had an online text-based affair with a woman who outed him to his wife for apparently vindictive reasons.

I don't know how we move this discussion forward into constructive territory. I see this at least partly through the lens of massive social changes disrupting the rules and neither side having a good play book. I challenge commenters here to find something constructive to say and avoid just wallowing in the mud here.