My (non-muslim) dad rants about politics frequently. I try to not fuel it, but the smallest ‘news’ brings up the topic. Advising him to not worry about things he can’t control is not appreciated. He needs to get it 'off his chest'. He can only rant to me, as there is no one else in the household.

Keeping your father company and listening to him is part of treating him well, even though he is not Muslim, so be patient and gentle with him and never harsh. If the talk turns to something forbidden like backbiting, excuse yourself kindly and come back after, and make du’a for his guidance. Also your good manners and companionship to him might lead him to Islam unless you see that this is not the case then don't let it harm your religion