I'm taking the parts of this write-up I don't have expertise with a grain of salt after seeig this.
Kessler cascades are real. Particularly at high altitudes. They're less of a problem in LEO. And in no case can they "[cripple] our access to space." (At current technology levels. To cripple access to space you need to vaporise material fractions of the Earth's crust into orbit.)
The sentence you mention was indeed a give away, but there are many others. Worst case scenario, nothing works and Elon burns a bunch of money, part of which goes into jobs and research. Best case scenario, we actually move away from technologies from the 50's and end up with daily, cheap earth-to-low-orbit (ideally something better than that - how about the moon?), no more whining about energy costs, and laser communication IRL. That's just the obvious stuff.
Being "realistic" and "having a budget" is what companies like Google do. That's all good, but we have enough of those already.