And copyright doesn’t give the ability to fight any of that is the point. This all sounds like abuse of DMCA process.
3Blue1Brown's logo is (probably) copyrightable, but the TED or Veritasium channel logos are (probably) not. If it could be claimed to be derivative of some other work, public domain or not, you may not fully own the copyright either. In general, it can be a big fuzzy grey area that needs a court to decide fully. Meanwhile, a trademark infringement would be easy to show.