Question on Alcohol Laws...

The rationale was that kids were allegedly running amuk,
or more precisely: were DRIVING cars amuk,
allegedly inflicting DISPROPORTIONATE fatalities upon the rest of the population,
while drunken driving on the nation's highways n byways
and that this was a defensive strategy to mitigate the carnage.

Still, I resent government using our taxes
to bribe State governments to screw us out of our freedom.

I do not believe that is a Constitutional thing to do.

Your source is right that the federal law doesn't prohibit persons under 21 from drinking, but it's wrong when it says that that the "national law specifically prohibits purchase and public possession of alcoholic beverages." It doesn't. It merely withholds federal funds from states that don't enact such prohibitions. The statute defines "alcoholic beverage," but it doesn't define "public possession." It would be the job of the states to define what it means to "publicly possess" an alcoholic beverage.