I definitely agree that you should be able to control what connections your own devices make. But we need to ensure that such control is only possible at the endpoint, since if it were possible at the router, then the bad guys could do that to censor other people's devices.
In your specific case, that means that while devices should offer a configuration setting for which DNS server to use, it shouldn't be via blindly listening to the possibly malicious DHCP server.
In your specific case, that means that while devices should offer a configuration setting for which DNS server to use, it shouldn't be via blindly listening to the possibly malicious DHCP server.