Investors are worried about a travel slowdown.Airbnb (ABNB -2.16%) is one of the most divisive stocks out there. Bulls think the company is revolutionizing travel and has many years left to grow, while bears think regulations and consumer pushback will lead to an "Airbnb Apocalypse." Bears look more correct this summer after the stock fell 13% following its second-quarter earnings release, when it highlighted slowing demand in North America.The stock is now down 47% from its all-time high. This sounds like ...