I've been trying to figure out why the term "liberal" so easily lends itself to being an insult. It can just be used without any other descriptive word attached to it, and still leave a bad taste in peoples' mouths. No context is needed in order for people to know that it is meant as a slight. "They are liberals."

And none of this makes any sense. You can attribute almost everything you have to "liberals".

You don't have to live as a slave, why? Liberals.
You don't have to wear a dress that covers your ankles or even a burka, why? Liberals.
You don't pay taxes to a king across the ocean who randomly sends his soldiers into your house, why? Liberals.
You don't have to believe in the national religion, why? Liberals.
You don't live in a communist dictatorship, why? Liberals.
You do not go to prison because you have a debt, why? Liberals.
You can vote as a woman or minority, why? Liberals.
You have freedom of speech, why? Liberals.
You are not locked in an institution if you suffer from depression or Alzheimer's, why? Liberals.
You have the right to a job or education no matter what your race, why? Liberals.

The truth is; every freedom or comfort you enjoy was fought for by the filthy liberals of some time past,  every group of people branded "Liberals" as an insult brought the change and progress that allowed us to become who we are now. The "conservatives" in each case are the group of people who less than 100 years later were to be branded hard headed, uncivilized, and primitive or short-sited, by history.

Why should anyone believe 'this time' it is a different situation? Why has 'liberal' persisted as a usable insult? Even in recent history there is no major fuck-up that can be attributed to liberal thinking that could be used as an example to keep people's hatred of the word alive. Where do we look for such an example? Kennedy's passing of civil rights bills, or the outstanding economy we had under Clinton's liberal economic plans?

Liberal, from latin Liber, free; the word once meant generous, tolerant. adj. 1, favoring progress and reform in social institutions, and the fullest practicable liberty of individual action. 2, tolerant. 4, not strict. 5, bountiful; generous.

I'm not sure how exactly this became a dirty word.

Right now people seem to think it stands for living in a hippie commune, not fighting terrorism, abortions for all, making prayer illegal or something like that, and allowing gay marriage.

So far allowing gay marriage is the only semi-accurate description of what liberal politicians stand for, and a lot of them are too conservative even for that, (much to my annoyance) including Barack Obama and Joe Biden.

We stand on the shoulders of radical liberals like John Adams, Benjamin Franklin, George Washington, Abraham Lincoln, and even Progressive Republican Theodore Roosevelt, and then curse their kind. We live in a nation founded on liberals, and swear allegiance's to a nation whose key word is Liberty, and then use the word as a pejorative.

I should point out that the definition of Liberal includes the word "practicable".  "favoring ... the fullest practicable liberty of individual action." Meaning as much freedom as possible without causing more harm than good. It's a balance right from the go. There's nothing about letting everyone do what they want no matter how much it hurts everyone else. Most Liberal politicians aren't even as liberal as their own supporters, and yet the label remains an image of politicians who want to turn American values on their ear.

Though in all fairness to the conservatives who cannot recollect a historical icon of greatness for their own, you can't have historical conservative heroes; just by the nature of the beast. History will never look at leaders who say "broken or not, it's as good as it gets and I don't want anything to change" as brave, heroic, or significant.