At work the other day, we got into a discussion about names. Weird family names, bizarre nicknames, the difference (if any) between your given name and the name you have now, and how that came to be.
We talked about how it's impossible to find a name for your child that will ensure he or she won't get picked on in school, and went around the table talking about what horrible mutations of our own names we'd been confronted with in our childhoods.
When it was my turn, I was able to rattle of a list of what I'd thought would be obvious disparaging forms of my own name: Retchin', Witchy, Retch, Bitchy, Bitchen...and that's just for my first name. Coworkers, however, were surprised. Of course they were-- they're all adults. If it had ever occurred to any of them to call me by one of those names, they didn't let on.
Whenever I see someone I care about deliberately referred to by the wrong name, even if it's a variation of their actual name that they just don't use, I think of third grade bullies. That, to me, is the level of maturity displayed by someone who uses this tactic of insult. Frequently it meant just using the dimunitive form of someone's name without their consent-- Mike becomes Mikey, Tom becomes Tommy, Sophia becomes Sophie, Elizabeth becomes Lizzy, etc.
Nothing's wrong with those versions of the names, of course, and sometimes the dimunitive version is even someone's given name. In other case it's chosen as an alternative by the name's owner. The point is, that's the person's actual name. That's what they go by. That's what they expect you to call them.
Warping a person's name into something they do not go by is condescending at best. You know this-- you've heard the tone with which Bob becomes Bobby to someone who doesn't like him. But doing so as a deliberate insult is actually akin to bigotry, I think.
Strong claim? Oh, definitely. But here's something to consider-- your first name at least is, in most cases, a circumstance of bith. In the same way that you were born Canadian or Australian, male or female, white or Latino, ectomorph or endomorph, you are very likely to have been born Jamal or Harriet.
Turning you into Jabba or Hairy-It is, then, pretty much like calling you fat or a ginger, or making fun of your accent. It's insulting a trait that the person (likely) didn't choose, can't do much about, has lived with for his/her entire life, and most importantly has no moral quality whatsoever. As circumstances of birth don't. If you don't like someone's name, that is an aesthetic judgment, a matter of taste. It says absolutely nothing about how good or intelligent or brave or educated they are. Or aren't.
It's funny that we call these things superficial characteristics, because in reality they go deep. Anything you've lived with for your entire life is going to be personal. Making fun of a lifelong "superficial characteristic" is trying to cut someone to the core over a thing unrelated to character, that they can do nothing about. That sounds an awful lot like bigotry, doesn't it?
That's why I don't think you should make fun of people's names. It's not because I'm opposed to insults-- not by a long shot-- but I'm opposed to that kind of insult.