If all organisms were infinitely adaptable there would be no extinct species.
This is a testable hypothesis. As it turns out, more than 99% of all species that ever lived on earth are extinct. Therefore, the hypothesis that all organisms are infinitely adaptable is false. From this, we can conclude that there is some probability greater than zero and less than one that penguins will go extinct rather than adapt given some environmental stressor.
It's not clear how this is relevant.
Invoking "the irrational mind" is problematic. All moral values are in some sense irrational -- due to Munchausen's trilemma coupled with the fact that an "ought" can't be derived from an "is" one simply cannot justify moral principles rationally. (Any attempt will be circular, inconsistent, or depend on unjustified axioms.) However, without moral values human beings would never engage in any sort of "rational" cognition in the first place -- you have to actually care about something before you spend time thinking about it.
Since no one can have a rational reason for caring about anything (OK, you might be able to rationally justify a sociopathic survival-based ethos) then it stands to reason that caring about the ugly animals would be just as irrational as caring about the cute animals. If that's the case, then why not focus on the cute animals since, as a matter of empirical fact, people already care about them more? Again, that it's "irrational" is irrelevant. Caring about anything besides your own survival is irrational.
(And as chenille pointed out, plenty of people are talking about less charismatic animals. This is a one-off blog post by a science journalist. The idea that you can criticize all discussion of climate change by pointing out that this blog post doesn't address the full scope of concerns about climate change is a little...hrrm, what's the word..."irrational"?)