You tell the companies you apply with that you don't want them to contact your current employer, and you will judge them on how good you keep their tongues tied

You tell the companies you apply with that you don't want them to contact your current employer, and you will judge them on how good you keep their tongues tied. And you mention the previous occurrences. Anyway, the point is, if your employer has employees looking elsewhere, they should be looking into what they need to do to make these employees' jobs better. The fact that the employer shares that these people are looking elsewhere doesn't reflect well.