You're not the first person to throw the word liberal into the conversation here in a demeaning way - you know, I expect that kind of black and white thinking from Americans (I lived in America for a while some years back and got thoroughly tired of this habit of theirs) but not from Brits. Just because someone is of a more liberal mindset, that doesn't make them some bleeding heart criminal sympathiser. Furthermore, just because you don't agree with their views, that doesn't mean they have no experience of real life - they simply have a different opinion on things.
Honestly, belitting people for having different views on various aspects of life is pretty poor behaviour, and is thoroughly unconstructive - in fact, it's actually damaging to discussion as a whole. By all means, disagree, but you can do so without belittling that person.