The difference is in the burden of proof. To be convicted in the criminal system the burden is "beyond reasonable doubt". In the civil system it's lower: "prepo

The difference is in the burden of proof. To be convicted in the criminal system the burden is "beyond reasonable doubt". In the civil system it's lower: "preponderance of the evidence". In the eyes of an HR department it's lower still. Theoretically, if you're arrested there's already "probable cause" - i.e. some evidence. It doesn't seem that weird or unreasonable that HR would act at this level. Does it suck if you didn't do anything? Yes. But people get fired for much less reason (or even no reason) all the time.