Harry saw nothing wrong with Moody being skilled at Occlumency.
As a veteran Auror, it made perfect sense for him to be skilled at magic that protected him.
In fact, quite a few of the professors at Hogwarts were skilled at this magic. Dumbledore went without saying, and Professor McGonagall was an expert in it too.
But the one who truly impressed Harry was Snape, who was currently lying like a corpse in St. Mungo's Hospital. His Occlumency had reached the point where it affected him from the inside out.
That dead face, which almost never showed an expression, and those emotionless, dead-fish eyes were probably side effects of taking his practice too far.
While Harry silently sniped at the former Potions professor, Professor Moody's demonstration continued.
"Many years ago, a great many wizards were controlled by the Imperius Curse," Moody said. Quite a few students in the class looked distinctly unhappy. They knew he was referring to the time of Voldemort's dark reign.
"At least, that's what they claimed. Ha, that gave the Ministry of Magic quite a headache. They had to distinguish between those who had been forced to act and those who had acted of their own free will. That was no easy task."
As he spoke, Moody returned the spider to its original size and put it into another jar beside him. "The Imperius Curse can be resisted. I'll teach you how in later lessons.
"But even if you know how, actually doing it is far from easy. It requires tremendous strength of character, or strength of soul, if you like. Not everyone can manage it. The best approach is still not to let it hit you. Vigilance! The best thing you can do is stay vigilant!"
By the end, Moody's voice had grown so loud