Denouncements?

The Washington Post reports that five passengers who boarded a plane yesterday at DFW were detained when they landed at Newark, basically for being foreigners:

Five airline passengers speaking in foreign languages and carrying "aircraft flight materials" were briefly detained Saturday until authorities determined they were returning to their home countries after attending a U.S. helicopter training school.

Note that "briefly", here, means "about three hours", as the article later says, and that what prompted the action was a report by passengers who were "suspicious of the men".

This isn't the first story of detention as a result of such reports. Aren't we emulating the "denouncements" of the communist regimes here? Is it reasonable to ask the random public to report "suspicious behaviour", and to assume that these reports have any credibility?