And yet it is possible and fine to define which topics belong to a community, and which topics do not.
Note this doesn't change anything about this group being political by your definition.
So if a group decides they only want to discuss cute cat pics, and specifically do not want to discuss social topics regarding humans (what people roughly mean when they express their antipathy for politics), that's one of many ways to make a cat community. It's still a political group in your book, necessarily. It's still not okay to talk about labor unions in that cat community.