There are two unforgivable evils (and numerous derivatives of those) that are allowed by the corporate business practice of requiring that new employees sign a statement which indemnifies past employers or other third parties.
The first is that any individual with sufficient cunning, wile, and manipulative ability could, with relative ease select a person of talent and begin a slander campaign until that person is fired. This attempt is self reinforcing because once it is started, the slanderer is at risk from the time the slander begins until the person of talents next engagement, which drives the slanderer to create worse and worse accusations. If the slanderer can succeed to develop a mythology that also keeps people from informing the target, then the slanderer can win emancipation from liability for the crime by waiting for, or even assisting the target in finding the targets next job with its accompanying indemnity.
The second unforgivable evil that is allowed by the business practice of blanket indemnity is the way it eliminates any possible benefit for right action when an employee is asked by an employer to commit a crime. In such a case, the right action for society is, of course, to report the criminal attempt of the employer to the police. However, with the business practice of providing blanket indemnity to third parties and past employers, an employer can fire any person that seems to be inclined to cooperate with the authorities, and then begin to slander said personages after indemnity is secured. Such a criminal employer would be eliminating any non-criminals not only from their place of business, but also any related business in the industry. Because of this, if an employee finds themselves asked to commit a crime by their employer, than the only way that they can act in their own best interest is to commit the crime, because acting in the best interest of society would result in complete loss of income.
I am searching for real world examples of these evils being put into practice. I suspect that I have been subjected to at least a derivative of the first of these but, I have little in the way of proof that defamation occurred, and I’ll bet that there are others in similar situations. However, in order to put together a reasonable case to get a law created to end this business practice, the existence of either or both of these evils needs to be proven severally.