Actually, that's logic. You don't need evidence for simple symbol manipulation.
What he states in that quote there is telcos call people hogs when they maximize their utilization of the connection they were sold. The telcos blame them for causing network congestion, ergo they believe that they cannot provide what they sold to their customers.
The telco T claims they can provide bandwidth B to the customer C. The average customer Q never uses what they've been sold, while the alleged hog H does, all the time at full capacity. However, H and Q are both subsets of C, the people guaranteed the bandwidth B. If T claims they cannot provide B to H because it affects Q's performance, this admits that T cannot provide B to all of C.
There's no part of that which requires sourcing, except perhaps the implicit understanding that it's not possible for a DSL customer to use more than the bandwidth that they were sold.