Fundamentally? Liberal beliefs are aligned with objective truths while conservative beliefs are aligned with ideology. Ideology is not beholden to fact. Therefore, conservatives are less concerned with facts.
I would add the caveat: In this country, in this political system, at this time. In other times and places it has been the other way around. The Joke deals with why the Communists couldn't afford to have even a slight sense of humor (because ideological purism crumbles under its own weight the minute any chinks in the armor are exposed). I think conservatism in America fits that paradigm at this moment. Modern small l liberalism is basically data driven, and this is driving the ideological inheritors of Reagan's Evil Empire worldview deeper and deeper into their caves, so much so that even the conservative ideas of yesterday (e.g. the ACA) are now some giant liberal conspiracy. I think rd95 is taking exception because he knows many conservative people who are just people, and refuses to believe that any group who is bound only by a common set of ideas can be lumped together with such a broad and horrible descriptor such as "tends to believe lies." I would like to weigh in and assuage his concerns by saying that is not conservatism per se that gives one this quality. It's blind belief in ideas whose maxims have not been able to stand empirical testing and are now disintegrating. Right now that describes republicans/conservatives perfectly.
Edit: But this is exactly why we should fear republicans so much right now. Crumbling ideology is what leads to totalitarianism. Remember that at first, the Soviets allowed elections in Central and Eastern Europe, because they were somewhat confident that the people would elect the proletariat. After the people discovered what a sham Bolshevism is, they rejected it, at which time the USSR started imposing their will militarily (e.g. in Hungary and Czechoslovakia).