Granted I only read part of the article, because on the whole I can't take the premise completely seriously. Its a premise that's nearly 40 years old by now.
Since the beginning of time, critics and outsiders have felt hip hop was vulgar and dangerous. They always said hip hop was hyper violent, misogynistic, drug addled, and dangerous. They feared that the acceptance of hip hop would raise a generation of drug dealers and murderers and destroy a generation.
All these assertions weren't true then and they aren't true now. The fact is that what goes on outside of hip hop is always a matter of the economy, crime prevention methods, and politics.
As far as flagging sales. Sales are down across the board. If your not named Taylor Swift, your not going Platinum. Its not possible. Where are the CD players? Why buy a CD when there are NO CD players. There's not one on new laptops, less and less new cars have them, there are no walkman's in store. There are no CDs. MP3s are easily downloaded for free, and more and more people see no reason to own the music all together and just stream it.
The demo that Hip Hop often caters too is also the Demo more likely to download. Young teens and middle aged people who are savvy enough to use a computer. Taylor Swift fans are pre-teens with parental protections on their devices and soccer moms who still actually own CD players and don't know how to download anything without getting a virus. Its an apples and oranges comparison.
Hip Hop still makes a positive impact across the Globe. Its about independence, its about Blatant disregard for authority, its about democratic ideas about what's hot and what's not within our genre. We don't have to train under a classical pianist to get respected and recognized, we dont have to go to Julliard. In your basement, you can make a global anthem. Hip Hop was among the music played in the Arab spring and protests across the world. Hip hop has sprinkled its influence into all the dance music that the world is obsessed with now. Half the DJs in the EDM scene are either Hip Hop DJs first or have explicitly worked with Hip hop figures. Alot of artists came up listening to Hip Hop, even the aforementioned Taylor Swift listens on occasion. Hip Hop is forever etched into the world. Hip Hop begat street artists like Banksy, whose painted street art on the Separation Barrier of Israel, It begat near billionaires like Dr. Dre and Jimmy Iovine, it begat a TV channel like Diddy's Revolt, its had a profound influence on Fashion houses like Ricardo Tisci and Givenchy.
If you only listen to what's on the radio and what may come up at 1 oclock am on one of the many MTV channels, then you may think its hard to defend hip hop. But if you only open the newspaper or randomly browse google, you will see Hip hop colored into everything. It basically raised the millenial generation. It blurred race barriers and genres. It's not hard to defend hip hop.