In my opinion? Yes, perfect characters are a bad thing, simply because "perfection" is completely impossible to attain in real life. Perfect characters to me are completely unrealistic and are boring to read because they have no flaws or issues to deal with, and you know exactly what's going to happen because, well, they're perfect.
However there's a difference between "perfect" characters and "morally good" characters. Characters can be morally good and still have imperfections. The video, for example, lists Luke Skywalker as a morally good character, which he is. However, Luke isn't perfect. In the beginning of the movie, he's shown as a whiny, self-entitled, typical teenager who just wants to go off and do his own thing. Throughout the trilogy, he grows more mature and learns from his mistakes, but even at the end he's not perfect. When he confronts Vader in the Emperor's throne room, Vader successfully provokes him to anger and causes Luke to go into a frenzy, nearly turning him to the dark side. Even though he's matured a lot, the fact that he was still able to give in to provocation and taunting shows he's not a perfect character.
He also lists Gandalf as a "perfect" character, but again, that's not true. Gandalf loses his temper too. "Fool of a Took! Throw yourself in next time, and rid us of your stupidity!"
The main reason I dislike perfect characters is basically that such characters do not exist in real life. Even Mr. Rogers, being a genuinely good person in every sense of the word, has done something wrong in his life. Everybody has. There isn't a single person on earth that hasn't done something wrong or that they were ashamed of. When a character is completely devoid of any flaws, he/she is incredibly boring to read and lacks any sort of creativity in my opinion. Why read anything about them when you know they're always going to do the right thing and succeed?
Like I said though, there's a difference between morally good characters and perfect characters. Perfect characters are a rarity in most forms of literature or media, simply because they aren't exciting. Think of the strangely popular 50 Shades of Grey (a book that'll I'll never understand how it became so popular) and the character Christian Grey. One of the main reasons critics panned this book (you know, besides having terrible writing and being extremely repetitive) is because the characters were "unrealistic." Christian Grey is, by definition, a perfect character. He's a Billionaire, speaks fluent French, is a concert-level pianist, a jet pilot, fully athletic, remarkably handsome, and is the best lover on earth with a huge, er... package. Oh, and all of this at the age of 26. The end result is a character that is flat, boring, unbelievable, and just not fun to read about.
In short, perfect characters are unrealistic, and by extension, not fun or exciting.