"Young professional" is what college educated white-collar/upper-middle class calls themselves. Because "white collar" carries a negative connotation with it these days in post white-flight cities.

The upper class and upper middle class are tired of living in the suburbs and want a taste of city life (mostly so they can get shit faced with eachother exclusively in some upscale city restaurant without the long drive home)

Normally I am ok with anybody living anywhere, but when white collars move back into the city, it drives the rent up and forces everyone else deeper into poverty or homelessness.