If anyone here has ever played a game that used Inca GameGuard, you know what I'm talking about. If you open a page in your web browser with a title that seems suspicious to GameGuard, it can fucking REBOOT your computer without warning! And that's not the only client with such problems. From my experience, it has been a problem shared by many anti-cheat clients: they're all a bit too trigger-happy, even though they shouldn't be holding that gun in the first place. And if that wasn't bad enough, these clients are also notoriously buggy. They will corrupt the state of your kernel (they will do things like overwrite entries in your SDT/SSDT, making various system calls fail; in fact, it's very common practice for some of these tools to outright disable the use of functions like NtOpenProcess or ZwWriteVirtualMemory, and then not even bother to reallow them after the anti-cheat client exits), they will litter your Windows folder, and wreak havoc however they want.
And here's the kicker: these anti-cheat clients aren't even that effective if you know what you are doing.