You're right - an economic downturn or financial crisis will crush juniors, and much worse than anything that would happen to most US stocks. It's virtually impossible for juniors to prosper when the rest of the market is floundering.

You have to remember that Peter's business is to promote juniors. Therefore, he would naturally have a positive bias regarding juniors - at least his clients. The conflict here is that he's thinking bottom-up for the juniors, and top-down for his macro economic views. Thus, a conflicting picture that doesn't make a lot of sense.