No, AT&T/VZW phased out unlimited plans because they realized that they could obtain more cash from heavy data users (legit or otherwise). They do this by inventing a narrative that somehow, it is the responsibility of end users to protect a "limited natural resource" that is restricted only by the fact that the carriers choose to defer infrastructure upgrades and
delay the incorporation of already-licensed spectrum on their networks.
And clearly, you drank the Koolaid.
"Abuse," according to most carrier-level TOSes that don't have ulterior price motives, usually entails using a network connection for illegal activity, or specifically using your bandwidth for the sole purpose of deliberately denying other users' access to the same.
If he was launching DDoS attacks, or spamming, or attempting to gain unauthorized access to other systems
then he's abusing the network.
If he was streaming audio/video 24/7 and not even bothering to watch it,
then he's abusing the network.
But if he was using netflix to legitimately watch movies, or listen to Pandora, then that's perfectly acceptable use of his internet connection.
Note that the top two wireless carriers are
making the case that their wireless networks are good enough to
replace wireline voice/data connections that they are refusing to repair after natural disasters. These same data usages are considered perfectly acceptable and non-abusive on a wired DSL, FiOS or U-Verse connection. So, it should not be considered abuse on wireless networks, either.
The only difference here is that if a user uses 50GB of data on anything other than a capped cellular data plan, they won't incur something in the neighborhood of $460 in overages. By rights, if this were truly abuse and truly a strain on the network, AT&T/Verizon should terminate your service to protect its core network. But they don't. They just happily charge you overage fees.
By the way, on an
average AT&T LTE connection, that 50GB download will take 9 minutes. How is getting charged $51.11 per minute of data usage not "abuse?"