I find it quite annoying when people name their project without consideration for other people in the open source community.
Other historical examples include Mozilla Firebird, which was renamed to Thunderbird after loud complains of the Firebird database community, or Twitter's Fabric, which clashes with Fabric (http://www.fabfile.org/), another Python project.
Indeed, a quick googling shows there's a Python Babel, an Eclipse Babel, an Emacs Babel, a TeX Babel, a Babel language, and an Open Babel for chemistry. I'm sure the addition of this new JS Babel won't inconvenience anyone too much.
If anything, I think the real issue is open source projects overplaying their hand and insisting they own certain words or ideas that they have no real claim to, particularly when there isn't any actual chance of confusion. The Firebird renaming wasn't so much sensible precedent as a good example of a Mozilla saying "okay please stop yelling, we'll do whatever you want".
Indeed, except that this project has nothing to do with i18n like (most of) the other projects you are citing. This is a compiler project, not a multilinguistic project.
2) There is nothing called "Python Babel", it's just called "Babel".
Eclipse Babel (https://eclipse.org/babel/) is called "Eclipse Babel" so there is no name clash.
For some of the other projects, you have a (minor) point.
3) "The Firebird renaming wasn't so much sensible precedent as a good example of a Mozilla saying "okay please stop yelling, we'll do whatever you want"."
Mozilla had a much stronger reason to comply than just goodwill and being fair: the other party had a trademark (see: http://www.firebirdsql.org/en/firebird-brand-faq/ ).
4) The considerate thing to do would have been to call the project "Babeljs".