Liberals have no principles. They are creatures of emotion, not logic. That's why it's both impossible and a waste of time to argue with liberals. It's like arguing with a child. You'd try to say something and make a logical point, and the child would just scream their same argument louder.
Liberals must be defeated, not convinced. It's impossible to convince them because to convince someone to change their mind, you must first assume that they are open to facts. Liberals are not. They go with whathever sounds nice and makes them feel good at the moment.