Ultimately its a youtuber's choice what they want to do and they have to live with the consequences of their actions afterwards. I personally would recommend keeping politics out of non political videos to avoid loosing viewers.
The simplest reason for my recommendation is that some people don't want to think about politics when they watch youtube videos on other subjects.
You also risk alienating viewers if your too political when you don't need to be. Note that I very much respect a youtuber's right to have a public politcal opinion. Provided that they don't put it in places where it doesn't belong.
As a real life example of why throwing politics into media where it doesn't belong can be detrimental to your "business": I heard a story about a theater group that did a Shakespearean play. It involved a scene with an assassination and for their version instead of accurate costuming they had Donald Trump being executed by women and minorities. The theater group quickly lost 2 sponsors (Delta Airlines and Bank of America) as result.
I respect the idea that youtubers, much like celebrities, can have a public opinion, but I don't like it when they bring it into places where it shouldn't be.