Ah, the typical debate with a liberal... They'll start off with some position that sounds good and/or is based on emotion. They'll be sure they are absolutely right, and start from the premise that you couldn't possibly right. In other words, closed-minded. Their supporting arguments are generally based on emotion not fact, often perception not reality, or idealism not practicality. When called on these things by an informed conservative they'll usually slide down one or two paths. They'll change the topic, attempting to divert down a side issue or away from the issue they're getting hammered on. The second tactic is to go after their opponent with personal attacks, perhaps questioning if they are informed, educated, biased, stupid, etc.
Debating/arguing with liberals can be fun if a little predictable. If you keep it all in perspective it can be great sport. By the end of the argument they'll go away angry and fuming and you can walk away with a smile on your face.