to weight gain.
Agree that 5,000 calories worth of nuts daily would lead to weight gain, but few, if any, could actually consume 5,000 calories worth in a day.
I think the main idea is that nuts generally don't taste good enough for most people to consume enormous quantities, even if they are relatively more calorie dense than other foods, so they don't deserve a bad label as "unhealthy" even if they have calories, are salty, fatty, etc.