Is getting a rec from a person like this acceptable?

How would Uchicago view

  • Someone that was my superior in a language building project ....

that is a successful political (left) activist


and I often debated them over politics during the project in a respectful way

https://collegeadmissions.uchicago.edu/apply/application/teacherevaluations

Being an activist isn’t a qualification.

That person happens to be an activist, but first and foremost, that person is a superior to me on a project initiative.

Read what Chicago says about who should write an LoR.
If you have that covered (it’s not clear if this is a primary letter or extra,) you can add a rec, but try to understand what value his letter would actually bring, vis a vis what Chicago looks for. See how Chicago words it in that link.

Make your best decision, but maybe talk with him, see if he knows what to write, what’s usually covered.

extra, and I do beleive that person can add an outside dimension

This opportunity likely qualifies as a supplemental rec. letter from teacher, employer, coach etc. If the activist/superior is a UChicago alum or has some other important connection to the university then it might even help the application, otherwise it’ll only help if OP believes it’s a crucial piece of the picture. But it’s likely not going to hurt and if OP was passionate about this project and the rec. will be enthusiastic then it makes sense to add it to the others. While no one knows the political affiliations of the reader(s), the same uncertainty would also hold if OP, instead, wrote about a political activity he/she was involved in and crazy about for the essay component. Or for that matter, a religious activity. But if it’s important to you, would you hold back because of what others might think? That doesn’t sound very “UChicago”.

Very true. It’s important, so I guess I’ll include it!