Kotkin definitely has an axe to grind with respect to "traditional urbanism". Among urban studies circles he's often criticized for his "anti-urban" (i.e. pre-automobile/highways urbanity) stance and his pro-suburban views.
If you read his works he seems to relish predicting the downfall of San Francisco (a Disneyland city in his mind) and Los Angeles.
He's certainly not as outright crazy as Wendell Cox (another noted anti-urbanist), but I certainly don't agree with much of of what he writes.
That's not to say all that he has to say is bunk. He usually raises a lot of good issues. But it is worth, as you suggest, noting some of his clear biases.
For example, this sentence is complete nonsense:
Gated communities are typically residential subdivisions. "Smart Growth" planning focuses on mixed-use development and walkable (to buy groceries, shop, work from professional offices, etc) neighborhoods.