israeli doc, thanks for the excellent quote. Related, in Reeh on lo titgadedu, R Hirsh writes that this applies to the community in general – we should not split in .. multiple agudot (same shoresh) instead of uniting all Torah-observant Jews. A great lesson for all debates we have – there is no mitzva in finding how to separate from others, only an aveirah.
I presume this comment was written before Agudah was formed, or maybe even inspired it.