You don't have to get it to be able to accept that others like it. Why not let them have their fun?
This sounds more as though you actively dislike anime than merely not seeing the appeal or being "ignorant". If you were to ignore it, there wouldn't be an issue...
Well, this is their personal project. You're welcome to make your own, or you can remove the branding if you want: it's open licensed. Or if you're not a coder, they even offer to remove the branding if you support the project
I don't get the impression that it's meant to be annoying, but a personal preference. I can't know that, though whitelabeling is a common thing people pay for without the original brand having made their logo extra ugly
Well, to be fair, that's not our doing so not really an argument for why one should accept something one apparently dislikes (I myself find the character funny and it brings a fun moment when it flashes by, but I can understand/accept that others see it differently of course)
They can have their fun on their personal websites. Subjecting others to your "fun" when you knows it annoys them is not cool.