Why don't Liberals stand up for themselves?

A friend posed this question with the idea that Liberals should fight back against Conservative style defamation of the Liberal character. My answer:

On the one had- if Liberals engage the Conservatives and fight on the terms set by the Conservative agenda it will be a never ending battle of wills because - well as you pointed out- the Conservatives have a way of manipulating the truth to sustain their base and cast aspersions upon the Liberal character. That form of psychological warfare has found a strong foothold in the Conservative Right due to the Christian Conservatives. Christianity has a long long history of conquering by manipulating the facts and just out right taking something and making it something else- and now that something like, say, The Crusades can physically never happen again it is all a psychological game. Now, that's not to say that all Christians are like this nor that all Conservatives are Christians. But the two ideologies have melded into this Godzilla creature that spreads it's intellectual dishonesty and perpetuate fear.
Honestly I'm one of those evil 'middle' folk. I embrace the literal meaning of conservatism as long as it was only applied to political ideology. I have no problem with being moderate and cautious and favoring the established values of our Constitution. Of course I temper this with a healthy dose of liberalism because I think that as times we need to be progressive in some arenas as well.
The only answer I have as to why the Liberals don't stand up for themselves is because , well, they're liberal. By nature they allow for a multifaceted world view and promote thinking for one's self and being free to make up one's own mind.
My question is why do so many in this country eschew intellectual growth and choose a life of fear based following rather than use their brains, view the empirical evidence and wake the hell up? Why are the members of the hardest working nation in the world so damn mentally lazy?