falsifying the idea of falsification

[Belacqua]

Actually come to think of it, im nothing, Karl Popper was the real Hiroshima.

This is funny, because I actually live in Hiroshima. On days when we're not hiding from viruses, I teach right at Ground Zero!

From what I can understand of the two papers I linked to, Popper's objections to evolution have been much exaggerated. I think this is understandable, since creationists will misuse whatever they can get their hands on. What Popper wrote, however, is nothing like denialism. You know this, I'm sure.

First he said that the principle of natural selection sounded like a tautology. 

there does not seem to be much difference, if any, between the assertion ‘those that survive are the fittest’ and the tautology ‘those that survive are those that survive’” (Popper 1972, 241–42).

[and]

Biologists (especially Fisher) felt compelled to define as “more fit” those which more often survive. Thus, what once looked like a promising explanatory theory becomes quite empty. The statement “Evolution tends to produce higher forms because only the fittest survive” may sound like an explanation. But if we substitute here for “the fittest” its defining phrase, we get: “Evolution tends to produce higher forms because those forms which more often survive more often survive.” So our “because” phrase has degenerated into a tautology. But tautology cannot explain anything. All tautologies are equivalent to “All tables are tables” or “Those who live long are those who live long.” (Popper 1994a, 54, emphasis added)5

[and]

“A central problem of evolutionary theory is the following: according to this theory, animals which are not well adapted to their changing environment per- ish; consequently those which survive (up to a certain moment) must be well adapted. This formula is little short of tautological, because ‘for the moment well adapted’ means much the same as ‘has those qualities which made it sur- vive so far.’ In other words, a considerable part of Darwinism is not of the na- ture of an empirical theory, but it is a logical truism” (Popper 1972, 69).

Note that this is NOT saying anything against evolution itself. It is only questioning whether there needs to be a fuller explanation of the mechanism. 

It certainly sounds as if he rejected the idea of it being a tautology later on:

The fact that the theory of natural selection is difficult to test has led some people, anti-Darwinists and even some great Darwinists, to claim that it is a tautology. . . . I mention this problem because I too belong among the culprits. Influenced by what these authorities say, I have in the past described the theory as "almost tautological," and I have tried to explain how the theory of natural selection could be untestable (as is a tautology) and yet of great scientific interest. My solution was that the doctrine of natural selection is a most successful metaphysical research programme. . . . [Popper, 1978, p. 344]

I have changed my mind about the testability and logical status of the theory of natural selection; and I am glad to have an opportunity to make a recantation. . . . [p. 345]

The theory of natural selection may be so formulated that it is far from tautological. In this case it is not only testable, but it turns out to be not strictly universally true. There seem to be exceptions, as with so many biological theories; and considering the random character of the variations on which natural selection operates, the occurrence of exceptions is not surprising. [p. 346]

He was also concerned that if natural selection is merely tautology then it becomes an a priori rule, rather than an empirical finding. 

He says that the empirical claims are these: the environmental conditions in which organisms live change slowly, organisms are sensitive to such changes, the only way organism can survive such changes is by producing mutations some of which respond to these changes, and useful mutations sometimes occur. Popper then describes what he thinks the a priori part of this theory is: “If the process of adjustment has gone on long enough, then the speed, finesse, and complexity of the adjustment may strike us as miraculous. And yet, the method of trial and of the elimination of errors, which leads to all this, can be said not to be an empirical method but to belong to the logic of the situation. This, I think, explains (perhaps a little too briefly) the logical or a priori components in Darwinism” (1972, 70). 

Since, he thinks, a priori rules aren't science, he wants to be sure that such things don't sneak in. 

To what extent he resolves this concern later on, and if he recants it thoroughly, I'm not sure of. As you say, it's a long paper. 

This should show, though, that Popper was never an evolution denier. He was working to make sure that everything about our understanding of evolution met strict scientific standards. One of the reasons we have such confidence in the theory of evolution is that it has been subjected to the most rigorous standards of judgment.

He also posited that evolution might occur through mechanisms other than natural selection:

we should avoid the mistake of thinking that NS [natural selection] is the only mechanism that can lead to apparently goal-directed adaptations. The way forward, he suggests, is to conceptualize alternative mechanisms and then design crucial experiments to decide between them and NS. We note that this is and has been common practice in evolutionary biology, where drift is often taken to be an important competitor to NS.

So he never denies that evolution happens, he only surmises that something other than natural selection might play a role. He hopes that scientists will design and carry out empirical tests on this subject. 

He also questioned whether the theory of evolution could be called a single theory, since evolution may involve a number of steps which differ from case to case, rather than every time a single series of events. He thought that it might be more correct to call it a "trend" rather than a "law." This seems esoteric to me, but as always the purpose is to make sure that what's happening is really science, really empirical, and really testable. And that we don't pretend we can do too much with what we really know. 

It makes sense that people would react strongly to anything that sounds as if it opposes evolution. Lots of stupid people have opposed it for stupid reasons. But Popper doesn't do anything like that. How his concerns played out over the following years I'm not sure. The long paper I link to has more detail.