If you are well grounded in the presentations of your own spiritual tradition, then it is unnecessary to be sectarian. But if you get mixed up about the various tenets and the terminology of different lineages, then you lack even a foothold in your own tradition.
You try to use someone else’s system to support your understanding, and get all tangled up, like a bad weaver, concerning the view, meditation, conduct, and result of the Path.
Unless you have certainty in your own system, you cannot use reasoning to understand your scriptures, and you cannot properly consider the assertions of others. You become a laughing stock in the eyes of the learned ones. It would be much better to possess a clear understanding of your own tradition.
One must see all the teachings as without contradiction, and consider all the scriptures as instructions. This will cause the root of sectarianism and prejudice to dry up, and give you a firm foundation in the Buddha’s teachings.