A reader once wrote to you about the way that liberals relentlessly employ the overlap fallacy: "Any Exception Disproves the Tendency."
Here are a few other tools I've found that liberals (and neoconservatives) frequently break out:
Argument from anecdote: Do I even need to give an example? The "apple pie" success stories of Mexican illegals in major newspapers will suffice to illustrate this sort of thing. Statistics are no match for sugar-coated anecdotes where liberals, neoconservatives, special interest groups, and open-borders libertarians are concerned. One of my favorite variants comes in the form of a rhetorical question suggesting that you need anecdotes of your own before you speak about an issue. Just mention the fact that the consequences of unrestricted Hispanic immigration are bothering you. Provide some statistics. Then (statistics be damned), the inevitable question is raised: "have you ever even taken the time to get to know Mexicans?" Not that they'll care what answer you give them.
Appeal to theoretical human potential: Actual human behavior seems to mean less to liberals than potential human behavior. I think this is one of the things that distinguishes liberals and neoconservatives from actual conservatives. For liberals, the fact that a person or people could conceivably do something often seems to be as good as if they actually do do something. Worried that Mexican cultural values are inferior to traditional Anglo-American cultural values when it comes to maintaining a First World country? "Sure, Mexican-Americans may not currently be as highly individualistic as Anglo-Americans, but no problem," the liberal will respond, "I see no reason why they couldn't be." The liberal is then happy to rest their case as if "could" solves the problem once and for all. They will simply ignore the reality that there is no force forcing Mexican-Americans to adopt such Anglo values. As a matter of fact, those traditional values are in decline among whites also. "But not to worry," the liberal might say, "we could regain those values if we really needed them."
Rubric argument: For this one, pick a relatively vague term like "social causes" and employ it as if it were something invested with a great deal more precision and explanatory power than it actually carries. One liberal commentator I came across on the internet indicated that because "social causes" could explain why women once did not attend universities in the numbers men did, that "social causes" could equally well explain why women did not comprise a high percentage of scientific and engineering graduates. What social causes is he speaking of? He didn't say, of course. He felt "social causes" was explanation enough.
The problem is that the liberal is combining a whole bunch of different things under the single rubric of "social causes" that may or may not have relevance to the issue. Historically there have been legal, economic, and familial reasons why women could not attend colleges. The fact that women now do in large numbers is evidence that none of those "social causes" apply today. Yet, even in the absence of those "social causes," women still make up a disproportionately low number of scientists and engineers. The very "social causes" the liberal refers to, far from offering an explanation of this fact, fail entirely to explain it. By appealing to a vague rubric the commentator disguises this fact and probably manages to fool himself in the process.
Squawk about qualifiers (and logical quantifiers) unnecessarily: Many liberals make a concerted effort not to understand what you mean. If I say that "young black men like rap music," in most circumstances I simply mean that "most young black men like rap music." I'm not ruling out the existence of young black men who don't like rap music. Even when it is abundantly clear that someone is speaking only in general terms, and even when common sense should be able to fill in the gap and qualify a statement, liberals rarely miss an opportunity to accuse someone of gross generalization when failing to explicitly qualify each and every statement on a politically incorrect topic. If you say, "blacks score lower than whites on IQ tests," some liberals invariably respond by accusing you of implying that "all blacks score lower than all whites on IQ tests." Of course, this never stops those same liberals from making blanket statements (often combined with horrible view accusations) about conservatives. "Why do those right-wingers continue to wage their war of hate against poor people in this country?"
The "Horrible View" Accusation: If you say that illegal immigrants are detrimental to American society, be prepared for preemptive accusations that you view Mexicans as Neanderthals or sub-humans. Liberals like to accuse their opponents of having horrible views of issues. I guess they employ this tactic because it is slightly more subtle than the plain old ad hominem attack while accomplishing pretty much the same thing.