It's not Microsoft's fault. I'm not a lawyer, but I'm pretty sure that you, the user, are the one who can be found negligent in a court of law should Microsoft seize one of your clients' confidential data and share it with one of their trusted partners or with law enforcement in a way that does harm to your client. That's because by simply using Windows 10, you agreed that Microsoft was allowed to spy on you, and through you, your client.