Profiling based on race or ethnicity is illegal. A checkpoint stopping people and checking their sobriety while on the road is perfectly legal, so long as is is reasonably effective in detecting and preventing impaired driving, and it is minimally intrusive to the driver. It's hardly a stretch to extend that to preventing weapons from being brought on to airplanes.
Actually this is not correct. Those "checkpoints" are officially called something along the lines of "informational stops" and are NOT (according to the State) designed to catch drunk drivers - stopping drivers without a reason other than to check if they have alcohol on their breath was ruled unconstitutional - so their purpose (the informational roadblock) is to allow the police to pass out literature to inform the driving public the dangers of drunk driving. If they happen to notice a driver who smells of alcohol then they can investigate further.
What the State doesn't tell you is that the driver does not have to roll down his window to talk to the officer. The officers are instructed to allow to pass any driver who waves off their request to roll down the window.
The Court of Appeals for MD created this legal fiction...the State doesn't tell you that you have the right to refuse to speak to the officer and the Media doesn't either....and the officers will follow you, after waving you through, to get PC if you refuse to talk to them.
Nice and constitutional, isn't it?