Why is it everyone wants to pretend this issue does not exist?

I'm not pretending that it doesn't exist. The biggest risk, IMHO, from copyright law is if PerlMonks makes a precedent of proactively enforcing the copyrights of third parties. It can make us liable if there are any cases that we fail to proactively enforce (which will surely happen, probably even if we were to hire a whole department to take on the task of researching and enforcing copyrights).

If we don't make such a precedent, then the site's legal liability is likely nothing until a notice arrives from a copyright holder. At that point, if we react in a timely fashion, then that should be the end of it.

In this particular case, I don't follow at all the logic of "remove the material". This is material that was pulled from the public internet. If there is someone with a strong interest in the copyright to it, then I'd expect their wishes to be that proper attribution and a link to the source material be provided. They seem very unlikely (IMO) to demand that the copy be removed. If someone had reproduced a substantial part of a book that is not available on the public internet, then the desire to have the material removed seems more likely (because they'd prefer that people pay for access to the material).

Also, for these particular cases, I doubt many of the (alleged) copyright holders have much interest in their copyright of the material in question. For example, I'd be extremely surprised if you can find any one of them that is interested in hiring a lawyer as a result of the alleged copying. But if they want it removed, then all they need to do is ask.

I don't believe that you know what they want and I don't think anyone benefits from making guesses about it. And I think the site has a lot to lose (by gaining a lot of legal liablility) if a policy of proactive enforcement of alleged third-party copyrights is followed.

As a published author, my concern with copyrights was mostly about making dang sure that I didn't include anything that was copyrighted by someone in my writing. I don't think that particular experience was very helpful in understanding the best policy for a site that accepts and publishes public submissions.

If you are concerned about copyrights, then contact the alleged owner and/or the alleged copier (the two parties that have both the power and responsibility to do something about it). Why does everyone want to pretend like they don't exist? They are the gorilla and the elephant in the room! If they don't care enough to do anything about the problem, then why should the site admins try to enforce the guesses of fourth parties as to what their desires might be? Such action doesn't make much sense to me. But, more importantly, in the similar scenarios I am familiar with, such action has been fundamental in creating very problematic legal liability.

I can see some people feeling dissatisfied with such a laissez faire policy; it being similar to an "I don't care at all about copyrights and so refuse to do anything about them" policy. Unfortunately, the legal system has repeatedly shown that caring and trying to help can be "rewarded" quite painfully.

At a previous company we were forced to not include (under advice from legal councel) nationally certified instructions for dealing with specific emergency situations. I don't think we were even allowed to point our customers to the specific resource, despite having implemented support for this type of resource specifically because many customers wanted to use that specific set of instructions. If we had proactively included or recommended that resource, then we would risk legal liability if someone died (etc.) while one of our customers (emergency services departments) was following those instructions. The emergency services employees would have legal protections that our company would not. I think even the creators of the instructions would likely have less legal liability in such a situation.

They've had to pass specific "good samaritan" laws in order to counter this legal effect for ordinary citizens trying to help out in emergency situations. But, if you get training as an emergency medical technician or similar, then you aren't covered by such and are advised to avoid helping out in an emergency when you are not on duty.

There is no "good samaritan" law when it comes to enforcing other people's copyrights that appear to have been violated by third parties based on advice from fourth parties.

So I'm happy to help deal with copyright violations but only in the manner requested by the copyright holder and only when the copyright holder requests it (at which point I'll likely just give the alleged owner the benefit of the doubt until such time as the alleged infringer escalates to the point of taking the case to a court of law and having the court tell me what should be done).