While this rep probably crossed a line that even Comcast's own training guidelines ostensibly prohibit, his behavior does not exist in a vacuum.
There is probably a "leaderboard" somewhere in his cube farm where agents with the highest retention rates are named and their competition tracked.
At monthly meetings, the agent who has achieved the very highest retention rates is recognized, lauded, and rewarded.
Agents whose retention rate is too low are given extra-training, poor performance reviews, and are eventually shown the door if they don't get with the program.
No agent is ever censured for having too high a retention rate.
Now balance that against what the company says its policy is about the aggressiveness of retention representatives.
I'm not saying the guy didn't act like a jerk; he may (possibly) be predisposed to such behavior by his character. I don't know him personally, so I can't judge his character at all.
But Comcast's corporate culture created the monster we listened to in that recording.