That's when you tell them they need to hard stop with the bad faith argument. That they literally admitted that the Democrats don't do it. That unless they have proof that the Democrats would do the same if given a chance then they can show it. Otherwise they need to give another argument as too why it's okay for Republicans to do this. Because otherwise the conversation is done.

Shut down, don't accept and call out bad faith arguments and actors. We MUST fight for truth and facts if we want them to mean anything. Never be afraid to call people out on their bullshit. Yet remember you maybe wrong sometimes. When and if proven wrong, own up to it. Thank them for helping you understand better and become a better, more educated person.