It was only a joke. He'd quipped that a manager's personality couldn't trigger an electric door. Those who were present chuckled. The observation was, after all, true. That accuracy may caused the remark to circulate far beyond the initial group.
There is no evidence that the bland manager ever heard about witticism but some of the manager's friends did and, blandness aside, their buddy was pretty well liked so they made a mental note to return the favor some day.
It was a small example of how matters can get blown out of proportion. Knowing both men, I believe that if the bland manager had heard the comment, he would have laughed. He might not have appreciated the humor but he wouldn't have wanted it to affect the other guy's career. He also knows he's not in the running for any charisma awards.
Sometimes though the offended party is not the one who was targeted.