Here's a story I made up:
Four people were attending dinner at someone special's house and they arrive in the dining room to eat. They sit down in their seats and the chefs bring out the main course. All four guests are eagerly awaiting to eat and when the food arrives to the table, they start to put the meat on their plate. They are about to chow down when one asks what they are about to eat and the host replies:
Each of the four guests has a different reaction to the knowledge.
The first guest is stunned for a second and when the reality sinks in, she stands up and storms out of the room while ranting about how awful it is.
The second guest is also outraged, but instead of leaving, he sits and eats the puppy. He is ashamed, but he doesn't want to make a scene like the first guest who he thinks is rude.
The third guest also eats the puppy, but he enjoys it. He burps and asks for seconds. He bites all the meat off the bones and makes puppy jokes. He looks over at the second guest and asks why he isn't enjoying the food and equates him with the first guest for not liking the puppy even though he eats it anyways.
The fourth guest looks at the meat and slowly stands up and leaves.
When the fourth guest walks outside, he sees the first guest still ranting. She looks at him and smiles.
"You didn't want to eat the puppy either?"
"Good for you, it's a shame the other two are eating the puppy."
"Yeah it is a shame...I thought they were going to serve kitten."
The first guest frowns.
Moral of the story: sometimes being right for the wrong reason makes you wrong. The first guest and the fourth guest agreed it was wrong to eat the puppy, but for different reasons. Because the fourth guest wanted to eat kittens instead of puppies, he is as awful as the second and third guests.
Now let's put in place certain ideologies to the guests. The first guest represents the liberals who are the only ones who are right. The second guest represents the "moderate" Democratic establishment, they go along with the Republicans on some issues like bank bailouts even though they don't like it and even criticize the liberals for trying to do the right thing. The third guest represents the Republican establishment and they enjoy doing the wrong thing. The fourth guest represents the far-right, the Ron Paul/teabagger group. They represent bad ideas also and only criticize the other groups cause they don't agree with their bad ideas. This is why liberals should avoid them.