They're right, to a point. At least if they're talking about revving an engine to warm it faster. WRT the pollutants, there are two significant factors that can lead to that. One is that the rings haven't expanded and don't seal as well, so fuel and oil can pass them more easily. Oil won't burn well or at all in a gasoline engine so you'll get a lot of gunk out the tailpipe from that. Also, catalytic converters don't really work until they're hot, so you're not getting the reduction of CO, unburned fuel/oil, or NOx. And like others have said, revving a cold engine causes much more wear because the oil is not as viscous and isn't circulated as well as when the engine is at operating temperature. So it does sound like they're pushing the kike line, but it does have some big nuggets of truth in it.