Making fun of things is actually really easy if you try even a little bit. Nearly anything can be made fun of, and in practice nearly anything is made fun of. This is concerning for several reasons.
First, if you are trying to do something, whether or not people are making fun of it is not necessarily a good signal as to whether or not it's actually good. A lot of good things get made fun of. A lot of bad things get made fun of. Thus, whether or not something gets made fun of is not necessarily a good indicator of whether or not it's actually good.[1] Optimally, only bad things would get made fun of, making it easy to determine what is good and bad - but this doesn't appear to be the case.
Second, if you want to make something sound bad, it's really easy. If you don't believe this, just take a politician or organization that you like and search for some criticism of it. It should generally be trivial to find people that are making fun of it for reasons that would sound compelling to a casual observer - even if those reasons aren't actually good. But a casual observer doesn't know that and thus can easily be fooled.[2]
Further, the fact that it's easy to make fun of things makes it so that a clever person can find themselves unnecessarily contemptuous of anything and everything. This sort of premature cynicism tends to be a failure mode I've noticed in many otherwise very intelligent people. Finding faults with things is pretty trivial, but you can quickly go from "it's easy to find faults with everything" to "everything is bad." This tends to be an undesirable mode of thinking - even if true, it's not particularly helpful.
[1] Whether or not something gets made fun of by the right people is a better indicator. That said, if you know who the right people are you usually have access to much more reliable methods.
[2] If you're still not convinced, take a politician or organization that you do like and really truly try to write an argument against that politician or organization. Note that this might actually change your opinion, so be warned.
Sure, many people use "I don't want to hear X" or "pfft, X is a well-known fallacy" or "you really should read author X on this subject and come back when you've educated yourself" or many variations on that theme to dismiss arguments they don't actually have counterarguments for. Agreed.
This ought not be surprising... any strategy that knowledgeable people use to conserve effort can also be adopted as a cheap signal by the ignorant. And since ignorant people are in general more common than knowledgeable people, that also means I can dismiss all the people who use that cheap strategy as ignorant, including the knowledgeable ones, if I don't mind paying the opportunity costs of doing that. (Which in turn allows for cheap countersignaling by ignorant contrarians, and around and around we go.)
None of that is to say that all the people using this strategy are ignorant, or that there's no value in learning to tell the difference..
Many knowledgeable people find frustrating being asked to address the same basic argument over and over. A common response to this is to write up the counterargument once and respond to such requests with pointers to that writeup. In larger contexts this turns into a body of FAQs, background essays and concepts, etc. which participants in the conversation are expected to have read and understood, and are assumed to agree with unless they explicitly note otherwise.
LW does this with a number of positions... starting a conversation about ethics here and then turning out halfway through to not accept consequentialism, for example, will tend to elicit frustration. Non-consequentialists are not per se unwelcome, but failing to acknowledge that the community norm exists is seen as a defection, and people who do that will frequently be dismissed at that point as not worth the effort. Similar things are true of atheism, of the computational model of consciousness, and a few other things.
It's not an unreasonable way to go.
My point is that there is a difference between an important FAQ and a bingo card.
Also, even with an FAQ one needs to be willing to engage in further discussion when people point out problems with the answers there, e.g., I don't entirely accept consequentialism (or many of the standard premises here for that measure) and have generally been able to have civilized discussions on the topics in question.