It's not a big deal that a bunch of so-called adults were using company time, data, and resources to act like elementary schoolyard bullies making fun of people's names?
Inevitably that sort of thing gets out, and insulting your customers' names is not really a great business strategy.
Beyond that, I wouldn't like working with people who are so clearly children. And not even good children.
It can't be bullying if the person (that would be bullied) isn't even aware of it.
Source: I was actually bullied as a kid. I couldn't care less if people are making fun of my name (or anything else about me) without me knowing about it.
If I found out someone thought my name was funny enough to make it on a list, I'd be curious and probably want to know more about why. Offense doesn't even cross my mind.
For example, you go to work and some of your more braindead colleagues are earnestly insisting that keeping a list of amusing customer names is the first step on the road to genocide.
Do you: (a) get involved in this nonsense, knowing from past experience how furious they'll get if you disagree, or (b) ignore this stupidity and get on with your job?
They were amused by a double meaning found in an arrangement of alphabetic characters.
It's really not a big deal.