The companies can hire whoever they want however they want within the law. They certainly could not hire this bloke.

However, if they want to hire someone who only has accusations against him, I don't see the problem. Businesses can and do hire full-fledged known criminals (typically after they've paid their legal penalty); and this is better for us all then having them uselessly sitting around. Many of them will still be perfectly good workers. Having done something illegal doesn't mean getting ejected from society; being accused certainly doesn't.

Slander - "Some statements such as an untrue accusation of having committed a crime, having a loathsome disease, or being unable to perform one's occupation are treated as slander per se since the harm and malice are obvious,"

https://legal-dictionary.thefreedictionary.com/slander

To be slander it would have to be provably false, not to simply be something that they can't prove to be true.

When a suspect is arrested for murder, the newspaper uses the words "suspect" and "alleged" in order to avoid slander lawsuits.

You can say that, but if he finds out, you can get sued for defamation. That's why most companies, when you ask for a reference, will not say anything beyond your dates of employment and maybe the names of the projects you were working on.

In reality, the majority of destructive rumors take the form of "Bob was impossible to work with", not "Bob sexually assaulted Avery". Meanwhile: a bogus accusation of rape is far more actionable than a bogus accusation of being an asshole; if you actually worked with Bob at all, you probably can't be sued for that at all, since things that can be construed as opinions cannot be the basis of a valid defamation claim. Unlike sexual assault, which, as a crime, is probably defamatory per se.

So relative to the set of all possible destruct rumors, allegations of sexual assault stand as outliers for how uniquely protected the accused actually are.