Let's talk about Dogen and secterianism.
I have often wondered how to interpret what people have called Dogen's sectarianism.
On the one hand Dogen was a consumate Ekayanaist (for ekayana, see here).
He was very opposed to Buddhist sectarianism and always said there is only One Buddha Venicle.
Then on the other hand he would criticise what some other teacher would say, or the interpretation of what another teacher (or school or lineage) would say.
Combining these two views his "One Buddhism" could then be seen as his saying only his lineage's teaching was real Buddhism. I think this last conclusion has been vastly overrated and overstated to come to the conclusion that Dogen was sectarian.
My conclusion is that Dogen was Ekayana in his view and that he always said that sectarianism in Buddhism was to be avoided -- and -- that when he criticised, he was not criticizing as a sectarian saying "follow me" or "follow my sect" but as a teacher trying to pull out the subtle roots of delusive views.
An important point is that being critical doesn't mean being sectarian.
May the force be with you