Someone may be called "perverse" according the Merriam-Webster Online Dictionary when they are "obstinate in opposing what is right, reasonable or accepted." I think we can maintain that certain philosophers are perverse but not, as may be anticipated or believed by some, because they hold opinions relating to conduct which are perverse. Would that they did concern themselves with conduct, but it is uncertain they would do so without first concerning themselves with what I think is the origin of their perversion. Instead, they are perverse because of their extraordinary (un-ordinary?) beliefs regarding reality. I refer to those philosophers who contend that we cannot know just what reality is; that what is real is unknowable.
What is immediately puzzling about these thinkers is that their conclusion appears to derive from what most would insist is real and which we rely on all the time, i.e. what is sometimes called "the evidence of our senses." They manage to twist "the evidence of our senses" into a basis for their conclusion by noting the unremarkable fact that we cannot always rely on our senses. Sometimes we experience illusions. Sometimes we see mirages. Sometimes we seem to hear things which cannot be heard by others. A pencil in a glass of water seems "bent." And so on and, regrettably, on.
The fact that we can rely on our senses in that they serve us well in acting and judging consequences in the great majority of cases, and have done so for hundreds of thousands of years, doesn't seem to impress these philosophers much. I think this fact impresses most of us, though, and that it does so for very good reasons. The only way we can reasonably judge their veracity is by testing the effectiveness of our senses, and the only way we can do that is by their successful employment in life. All in all, they work rather well.
When they don't work well, there are usually perfectly good explanations readily available, which need not be dependent on the belief that what is real is unknowable. We may be hallucinating because we're feverish. We may be mistaken, and find on further consideration (closer examination or investigation) that we were mistaken. We may not know or understand everything about the universe yet.
It requires a rather extreme disregard of the reliability of "the evidence of our senses", and otherwise plausible explanations for the instances when they "deceive" us ("deceive" is of course a very loaded word) to infer that we cannot know what is real. I think someone who comes to that conclusion may justly be considered obstinate in opposing what is right, reasonable and accepted and therefore perverse.
As always, I wonder what it is that causes this strikingly persistent perversity. Sceptics have been with us since ancient times, when philosophy as we know it first began, and there are famous examples of philosophers who have managed to convince themselves that what is real is unknowable, if not that there is no "real." They litter the history of thought.
They seem in their philosophy to be disconnected from life. We've no reason to believe that they lived differently from those simple folk who cheerfully felt that they were interacting with the real every moment of their lives, however. This makes one wonder whether, as philosophers, they were participating in a willful disconnection, deliberately separating their philosophy from their lives. If that's so, what would induce them to engage in such a futile task? Perhaps even more interesting is the question why we continue to study them, and even to follow them on such an impotent path?
Are our lives so dreadful? Is the task of bettering ourselves and our lives so daunting that we turn from it, convincing ourselves that we can't know what is the case?