... because a single website with tons of alternatives does a small protest action you don't like you're not going to contribute to the entire project anymore? I honestly can't understand that.
Wikimedia Germany is also legally seoparate from the Wikimedia Foundation, and still everyone considers them the official German offshoot.
They represent OSM in Germany, they think it's in OSM's best interest to draw attention to this issue, they do so on their own website, leaving all tile servers etc alone. I can see being momentarily annoyed at it, I can see disagreeing with them (politically or if that's a useful protest form), but I don't see anything that would count as a gross violation of trust or something that's out of scope for a local chapter to do.
FTFY
[0] https://wiki.openstreetmap.org/wiki/They_are_using_OpenStree...
[1]https://wiki.openstreetmap.org/wiki/List_of_OSM-based_servic...