Despite their professed desire for civil discourse, rational debate, and the like, liberals rarely ever actually debate reasonably. Sometimes they try to and fail for lack of ability. But more often, they use a variety of tactics that serve to stifle debate rather than foster it.
These tactics should be recognized for what they are. Thus follows a list of the most frequent anti-rational tricks employed by liberals.
Ad Hominem Attacks
Ad hominem means against the person. Such an attack is directed against a debating opponent rather than against his argument. It seeks to discredit the source of an argument or discourage him from making it rather than respond to the argument. It is a rational strategy for someone who cannot refute an argument.
"You're a [racist, sexist, homophobe, xenophobe, fascist, etc.]"
Black conservative economist Thomas Sowell defined a racist as a conservative who is winning an argument. This is a specific form of ad hominem attack. These are all emotionally charged epithets. Using them serves to redirect the argument to whether someone is such things. They are used to avoid the issue of what the conservative says is true.
"You're an extremist."
Whether some political belief is "extreme" is hardly important compared to whether it is correct. Alleging extremism avoids the real issue. Many political beliefs that today are considered obvious were once "extreme" positions, including human rights, abolition of slavery, and women's suffrage.
Statements like "you're all wrong" give the appearance of debate without containing any substance. They are used to try to cast doubt upon an argument. They don't contain any specific assertions of fact or logical arguments that can be subjected to scrutiny.
Claiming to be offended redirects the debate to whether some statement is "offensive," rather than whether it is true. It creates a moral stigma against the discussion of certain issues and the expression of certain opinions.
"I demand an apology."
This redirects the debate and makes the issue whether an apology will be given and whether one is warranted. The real issue is whether the given statement is true.
Political correctness makes certain topics and opinions off limits by creating a psychological climate of disapproval of their discussion. It mandates the use of convoluted and inaccurate language to hide the truth.
People who have been seriously injured or have lost a family member make political statements. It is deemed insensitive to criticize them due to their victim status.
This one claims that people in some group have no right to speak on a given issue because of who they are. Examples include claiming that men have no right to oppose abortion, whites have no right to oppose racial preferences, and non-veterans have no right to support military action.
Separation of Church and State
As used by Jefferson, this means that government may not create a state church or discriminate based on religion. But liberals use this to say that religious people have no right to be involved in politics or advocate their ideas. This only applies to conservative ideas, not the religious left advocating liberalism.
Change the subject
If you can't refute a given argument, change the subject. Bring up a completely different subject for which you think you have a stronger argument. For example, bring up Iraq during a discussion of environmentalism.
Attack a straw man
If you can't refute an argument, make up a different argument that you can refute. Attribute it to your opponent. Ideally, it should superficially resemble a real argument, using many of the same words. Bonus points for extra outrage.
"Your source is a conservative."
Use the fact that your opponent's source supports his conclusion to argue that it can't be trusted. Don't provide any evidence that the source is unreliable.
"There's no absolute truth."
This is last resort for someone who can't defend his position. The claim that "truth is constructed by those with power" allows a liberal to ignore all the logic and evidence in the world. This postmodernist philosophy is plainly contradicted by how people live their lives, whatever they say. Reality will catch up with them, eventually.
The fact that liberals regularly employ such debating tricks suggests that they are not serious about desiring "civil discourse." For some reason, they continue to hold beliefs that they cannot openly defend.