They don't want to change the name, possibly because they have different priorities than you. It is what it is. Deal with it.
I understand their "rights," it is absolutely their choice. But...
It has been this way for a long time, but what they don't understand is they could very likely be doing greater good to stick it to, e.g. Adobe with just a little bit of humbling, which would buy a whole lot more popularity and acceptance.
And I actually agree a different name would be in the project's best interests. But I also accept that reasonable people can disagree, and that I'm not the one maintaining GIMP.
Free speech, et al, means I'm absolutely allowed to be annoying if I think it's worth it.
But please, show me a project you worked on, and I will show up to forcibly demand a change you don't want every single time the project comes up. And I will guarantee you that very quickly you will find it exceedingly tiring.
I think my problem with your analysis here is that it's like "a personal project."
It's not. It's GNU software. And to me -- choosing to use a license like that is something like taking up a mantle of freedom. You're part of something bigger, and I can't imagine that wouldn't include discussing out loud what direction the software should take.
Your interpretation -- which you didn't even specify! Many folks won't even know what you're talking about! -- is not the default in my experience. I usually think along the lines of "lame".
In other words, your perspective is the one that seems childish to me.
And while I also do bristle a little bit at the general thing of "lets change the name because someones offended," I also understand that it's always a weighing test.
And here, given Adobe's traditionally damn near absolute chokehold on this space, I absolutely believe that, had they changed it a long time ago -- we could all be in a better place here.
Again, hope it was worth it.
For me the main reason why I dont use GIMP is missing features and how its ergonomics are worse than photoshop.