Colleges across America have indulged in blatant racial segregation in their dorms for decades — yet only last week did the feds start to make a stink about it. Sure, it’s liberal racism — but “no whites allowed” offends the Constitution every bit as much as “no blacks allowed.” And this (relatively) innocuous segregation , practiced on half the nation’s campus, is only the tip of the iceberg of the plainly pernicious racism plaguing US higher education . “We’re trying to do good” doesn’t