It's surprising that a professor of economics would state that the "The college tuition bubble makes the housing price bubble seem pretty lame by comparison". If you're looking at the numbers alone yes the graph looks pretty scary. There are explanations outside of a speculative bubble for why a degree has gone up in value so quickly. Over the time of his graph the percentage of those seeking degrees has doubled (15%-30%), while home ownership has remained relatively flat (62%-68%). Prior to 1978 a good union job meant you were solidly middle class, in the 80s that changed you had to get a degree to be middle class. In the 90s it accelerates again as even non-union manufacturing jobs were shipped overseas (and foreign students shipped in).
The housing bubble was entirely speculative. It was stoked by the fed keeping rates low, later fear took over as people didn't want to be either 'priced out forever' or miss out on easy money.
As others have mentioned it's apples and oranges, you can not sell nor live in a degree; defaulting on your student loan will not render you homeless. The bubble and collapse in house prices is far more signigicant to the larger economy. The housing market is measured in trillions, student loans in billions.
Don't get me wrong tuition is way overpriced for what you get. A drop in tuition and house prices would do everyone good.