It's not only in commercials. When I was laid off, I worked a stint at the Home Depot. In the training videos we watched for operating the lift equipment, they always showed a white guy doing the safety violations - smoking a cig while changing the propane tank, etc...
I was in Government - in all of the sexual harassment videos. the white guy was always portrayed as the aggressor, the female, the minority, etc. never committed any sexualy harassment violations = it was always the white guy.
In fact, at one session, the facilitator actually stated that sexual harassment is a problem of the white male that needs to be addressed.