Good to get his side of the story, but everything has to be known as alleged: we don't actually know (yet) whether there actually was a consensual relationship before the accuser joined Square, for instance. It's a fairly convincing defense and good tactics to get this out there immediately to the public mind--and it rings as pretty plausible for me--but it's still just a claim that might just be cleverly engineered to protect Keith.

Edited to add: There's also the altogether not-minor point that even a consensual relationship preceding and concurrent with Square employment wouldn't mean sexual harassment was impossible. Imagine the accuser, say, breaking up with Keith and getting stalked or threatened by him as a result.