Arrogant, vindictive sectarianism has nothing to do with spirituality; All philosophical systems should be studied without bias.

Patrul Rinpoche

(from "Enlightened Vagabond: The Life and Teachings of Patrul Rinpoche"):

Patrul was famously nonsectarian, never praising some schools and disparaging others. He refused to fuel the arrogant, vindictive sectarianism that had long been rampant in Tibet. Patrul advised Nyoshul Lungtok: “Study all philosophical systems without bias. Bias creates distorted understanding. When you study all teachings impartially, you will know what is true and what is not, you will know what is profound and what is not, you will know what accords with the buddhas’ wisdom-mind, and so forth. From then on, understanding will come through your own insight.”

Once, Patrul’s wanderings took him on a road that passed by Dargye Monastery, a Geluk monastery in the Trehor region of Kham. Now, the monks of Dargye Monastery were notorious for their sectarianism. They used to harass all passing travelers, demanding to know which school they belonged to — Nyingma, Kagyu, Sakya, or Geluk. When they found out someone belonged to a school other than their school, they’d insult him rudely and sometimes beat him up.

When Patrul came walking near their monastery, three huge, fierce-looking monks approached him and demanded roughly, “Which school do you follow?”Knowing they were out to pick a fight, Patrul replied tactfully and yet with perfect accuracy, “I follow the school of the Lord Buddha!” Unsatisfied and still intent on determining his school, they went on, “How do you recite the refuge formula?”

Patrul recited: “I take refuge in the Buddha, the Dharma, and the Sangha!” His answer gave the sectarian monks no satisfaction, as they were expecting refuge verses that would reveal Patrul’s affiliation to a particular school and lineage.

“Name your tutelary deity!” they demanded, with increasing annoyance. “The Three Jewels!” replied Patrul patiently. Desperate for an answer, hoping to discover his school through his initiation name, the monks shouted, “Reveal to us your secret name!” Now, it so happens that in Tibetan, the phrase “secret name” also refers to the male organ. Lifting up his robes, Patrul amiably replied, in nomad dialect, “Bulu-bulu!” (“Dick!”)

That finally shut them up. Patrul at last was able to continue on his way, unmolested. He did so, loudly reciting, “Om mani padme hung. Om mani padme hung.”