They were describing an alternate explanation of the cause of the problem, not a solution. And yes, an activity can go from being not a problem to a problem whe

They were describing an alternate explanation of the cause of the problem, not a solution. And yes, an activity can go from being not a problem to a problem when poor people start do it because there are a lot more poor people than rich people. 1000 people doing something will cause a lot more wear and tear than 10 people. Also, with greater numbers, there's a greater chance of one of them being a thoughtless jerk who causes harm.