>>”How to Stop a Liberal from Talking”<<
Confront him with facts.
If you confront them with facts they just start with the ad hominem attacks. Emotion is where they retreat to when confronted with objectivity, and it is usually ugly.
Examples:
Abortion: ask them when someone becomes human. Most will say at third trimester. But not if the mother doesn't want it. Then facts are based on feelings.
Global warming: Ask them why are we worried about global warming in the coldest part of the Quaternary Ice Age at the end of our interglacial period while we are at dangerously low levels of CO2. They will look at you like they never heard any of that before and go on with some nutty ideas that we are out of the ice age when even the global alarmist don't believe that.
They drive their 'facts' based on feelings.
That's never worked for me, usually resulted in the yelling and stomping off in a huff. So I guess technically you are right - they stop talking, at least to me...