[GianFabien]

Based upon your expressed concerns, it appears that you are currently operating a Windows-free environment. I presume from your question that you have a (potential) new hire who wants to bring their Windows laptop and connect it into your environment.

If these assumptions are correct, then in the interests of maintaining your secured environment and avoiding support issues you have a valid reason to ban such Windows laptops from your workplace. The new hire should be issued with a correctly configured PC.

If the issue has arisen during negotiations with a new hire, then it's up to them to walk if they are so attached to their Windows devices. Is it some new manager or sales person? If they can't handle working in your environment then they will be more trouble than they are worth.