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I have a coworker named "Bob" (not his real name) who keeps insisting that I call him "Shah". I don't think it's right that I be required to use what seems to me to be a silly pet name; the guy is already extremely creepy. He says that he "feels like he's being punished" when I call him "Bob". We work for a very large professional engineering company; am I off base here? I'd really like to know what others have to say about this. Thanks!

You should just call him the name that he prefers to be called as.

It is not for you to decided.

My legal name (bank, tax etc) is Edward. But everybody else calls me Ed. That is my choice. Would you not like to be called some other name apart from your preferred name?

It depends on whether it's really a nickname that he always goes by, or some sort of power trip or strange form of harassment targeted only at you. Assuming none of those unlikely factors are in play, you should call people by the name they choose to go by.

While most workplaces are on first-name basis by now, you wouldn't persist in referring to a colleague by their old name if they adopt a new last name after marriage either. The general rule when it comes to names is that people get to decide what they would like to be called. Within reason of course, slurs or overly grandiose nicknames are often frowned upon. But good managers will quickly put a stop to those shenanigans.

So in regards to your main question: you are indeed off-base here. If this is simply the name that he goes by, that is for all intents and purposes his "real name". In some countries he wouldn't even require an official name change. So in this case you should simply do the professional thing and use the name he'd like you to use.

This situation is trickier if it's a nickname only used within the team. If that's the case this is more about team dynamics and fitting in than it is about respecting professional norms. But if your entire team calls him "Shah" then it would likely be best to join them in that.

There's some useful reading on a related question "How to stop nicknames from being used?"

You are not obligated to use a silly pet name. You could let him know that you are uncomfortable calling him Shah and that you will either call him Bob or a more reasonable nickname like Rob or something else closer to his real name. If he continues to insist and will not agree to a more reasonable name then just keep calling him Bob. You should not get in trouble for using somebody's actual name even if they prefer a nickname.