Fine; it's the paint by numbers of the hardware world. Oh, and it's really expensive to boot. Raspberry Pi's and Arduinos are for hobbyists; this is a child's toy.
If anything, you would think that you'd be overjoyed. People would hypothetically try to create products with these "child's toys" and give people like you a more robust job market and salary prospects. Or they wouldn't and it doesn't affect you at all.
I agree with the facts and premise he presents. A Tessel is a toy. It is not going to teach you C, Assembly, or any of the realities of hardware development.
I disagree with the premise that this is a bad thing. I disagree with the premise that people are buying Tessels with the intent to create production grade products. This is literally a toy for people who want to screw around with hardware. This is not a bad thing.
Would you give people shit for buying some Lego Mindstorms to do the same thing instead of a Tessel?