Yes, when one person controls virtually everything, and can't suck it up on something based on taste, they're usually being selfish and petty.
It can be. I don't think when I have put such limits in my games I was being particularly petty. Selfish, a bit, sure.
For example, I'm starting a new Warhammer Fantasy Roleplay 4e campaign for a group of players that I've been playing DnD 5e with for years. None of them have played Warhammer before.
One of the players asked if he could play a vampire because he read online that this was an option.
I said that it might not work well with the setting and the game I was going to run but I would look into it because there were no options for it in the core rules. Under some of the lore there were examples of vampire that could possibly make this work, but the only mechanics for a vampire character were in an older edition's rules and, even there, it was highly discouraged (kinda weird--hey here are some rules to do so, but you probably shouldn't

). It seems that even in that older edition setting, the rules were more for an entire party to play vampires in a vampire-centric game.
Even then, I could see working with this, but there was no mechanical support for vampire characters in the new edition. I did look into how I could convert the older rules into the newer rules. It didn't seem like it would be too difficult. But, one reason I wanted to run WFRP4e is the excellent Cubicle7 modules for Foundry. So not only would I have had to convert an older edition's class to 4th edition, I would have had to try to kludge a custom class in Foundry.
I finally told the player that this was the first time I was running this system, the adventure location and story was not well-fit for a vampire character, and I was worried that having to mess around with custom classes in Foundry creating issues with the automations etc. It just was not something I wanted to deal with right now, but we can revisit after I've had time to get more comfortable with the new system.
So, basically, it was a "no." It was a no BECAUSE I control everything and would have to do a lot of extra work that I just didn't want to do when I was starting a new campaign with a new system. My decision was certainly selfish, but I certainly do not feel that I'm being petty.
I've also run D&D campaigns with strict race and class limits due to my homebrew setting. That may have been more on the petty side. But I think that is stretching the definition of "petty." When I have spent a lot of time creating a world that I find interesting and would like to share with a group of players, I'm not adding limitations to spite the players. Whether one feels that my limitations are trivial or small-minded depend on whether you value my work and vision for that world or just roll your eyes and feel I'm taking my make-believe game world too seriously. I'm certainly selfish in that this is what I want to play. I don't see it as any more selfish than inviting people over to engage in any other social activity.
I've run and had fun with anything-goes campaigns, but I don't always want to run those kinds of campaigns. It may be selectively selfish, but it feel like an exaggeration to label these choices as petty.