As a middle aged couple we are never stopped by customs and even the immigration officers are mostly polite. When I was a youth I was often stopped so I guess that's what's happening to your son. He may use 'harassed' in a different way; it sounds like the word young people use for anything that stops them doing anything they want!

My middle aged brother in law has a long pony tail and is almost always stopped so I guess there is a certain amount of selection by stereotype going on.