I agree the example in the piece is a bit extreme, but was just trying to make a point. It is very possible to have a provocative thumbnail that is relevant to your video. I definitely don't advocate deceiving your audience.
"Maybe you don’t need to be this extreme, but your thumbnail should be interesting..."
I do agree with about everything else in the article, it is just the reinforcement of behavior that is a personal pet peeve of mine got a knee jerk reaction. I think "thumbnail fixing" is the 3rd largest problem on Video Sharing websites behind Youtube's comment threads (#2, I had to squeeze that pet peeve in).
Now, when it comes to a provocative thumbnail that is relevant to the video...great advice.
Edit: By "I agree" I mean I feel comfortable taking your advice. Good read.