One the things that kept Simone Weil, that most orthodox of non-Catholic Catholics, from being baptized and partaking of the Eucharist, was what she saw as the rejection by the Church of eternal Truths as expressed by other religions. A Christian Platonist, she learned Sanskrit in order to study the Hindu scriptures, particularly the Bhagavad Gita, in their original language.
I am currently reading, at the pace of about two pages per day, The Way of the Sufi by Idries Shah. The quote below expresses very well, I think, the dangers of orthodoxy and organized religion to the quest of the spiritual pilgrim:
All religions, as theologians – and their opponents – understand the word, is something other than what it is assumed to be.
Religion is a vehicle. Its expressions, rituals, moral and other teachings are designed to cause certain elevating effects, at a certain time, upon certain circumstances.
Because of the difficulty of maintaining the science of man, religion was instituted as a means of approaching truth. The means always became, for the shallow, the end, and the vehicle became the idol.
Only the man of wisdom, not the man of faith or intellect, can cause the vehicle to move again.
It is my understanding that the "man of wisdom" referrred to in the final sentence is a teacher, or spiritual guide--a guru if we want to admit that much-abused word. I do not take it to mean that men of faith, or even intellectuals, are forever barred from the Kingdom.
Sufism, which is often understood to be the "mystical expression of Islam," is similar to Christianity in its emphasis on love. This would seem to position it well as a possible mediator in the current troubles between Islam and the West.