Let's dispense with the theatrics. Having a relationship with someone in your chain is not even close to sexual harassment. Yes, it can lead to it but generally it doesn't. It's not at all illegal either.
When I entered the workforce not so long ago most companies didn't even have policies against it. My university didn't make a policy about it until 2012. I know a very happily married couple who got married this way (a little earlier - perhaps around 2006 or 2007). I don't think they'd be happy if I referred to their behavior as "sexual harrasment".
I think it's a good policy and it's fair they enforce it, but equating it to sexual harassment is nonsense.
You can't prevent people from having relationships. It's not realistic. My company has specific rules about this. Typically, "problematic" relationships need to be disclosed to HR and leadership, but they're not forbidden per se.
They may not think about it that way, but if one of that couple got a promotion from the other then every other person on the team pretty much has grounds for a law suit. There are reasons these rules exist, and the CEO of a high profile company has no excuse not to know them all.