It is perhaps ironic that the vast bulk of opposition to Masonry, then, is from those who would claim that it is in fact a religion. The fact that Masonry is not a religion -- and that it's OK for it not to be a religion -- is perhaps the most difficult thing to explain to a non-Mason. I've seen many very learned men unable to comprehend the distinction. So it's with some hubris that I'll attempt to explain my view of it here, to assist some brother in weighing the arguments should the need arise.
That Masonry does not exclude or teach any particular religion is simply a fact. Here's what Albert Pike says on the subject, in context:
The great truth it inculcates is, that notwithstanding the existence of Evil, God is infinitely wise, just, and good: that though the affairs of the world proceed by no rule of right and wrong known to us the narrowness of our views, yet all is right, for it is the work of God; and all evils, all miseries, all misfortunes, are but as drops in the vast current that is sweeping onward, guided by Him, to a great and magnificent result: that, at the appointed time, He will redeem and regenerate the world, and the Principle, the Power and the existence of Evil will then cease; that this will be brought about by such means and instruments as He chooses to employ; whether by the merits of a Redeemer that has already appeared or a Messiah that is yet waited for, by an incarnation of Himself or by an inspired prophet, it does not belong to us as Masons to decide. Let each judge and believe for himself.To paraphrase: We don't know why bad things happen to good people, or good things happen to bad people. Our view isn't broad enough to perceive the whole of God's plan. Nevertheless we believe there is one, and all things will ultimately lead to Good. But we as Masons neither teach nor deny any particular doctrine beyond that. We leave that to the faith of each individual.
The reason that "it does not belong to us as Masons to decide" is precisely because Masonry isn't a religion, and it's composed of members of many religions, each with their own tenets of faith. Because it is inclusive; because it is tolerant, we're not going to pressure you to change your mind on your faith. That is not our purpose.
And it is important to note that each Mason is an individual. No book and no essay speaks for the whole of Masonry, Pike's work included. Each Mason speaks his own mind. Among us, each opinion is judged on the weight of its merit, not its authority.
Now, let's discuss that bit about "purpose" for a second. I'm going to use as an analogy a court of law. There are strict roles to which the officers of the court adhere, whether it be the judge who presides, the attorneys, the court reporter, the bailiff, the jury, or the gallery. There is a gavel by which the judge opens proceedings and signals people to rise or sit. There is a Bible upon which oaths are taken; and should a witness be of another faith, another book, important to the witness' faith, may be employed. Some courts are opened in prayer. The judge is addressed by an honorific ("Your Honor" in the US; "Your Worship" in the UK). Often the judge wears robes. The proceedings are conducted according to prescribed ritual. A court of law gives every outward appearance of a religious ceremony.
And yet... the jury is not a choir. The judge is not a priest. The Bible is not used exclusively. The oaths are not sacrilegious. And though the purpose of Justice is aligned with Divine will, it is for the secular purpose of Justice that the court is convened. Within the proceedings of the Court, religious affiliation is irrelevant; it is deliberately ignored save for certain universal principles like Justice and Equality.
The Court does not exist to reserve Justice for only those who follow Mosaic Law. Its officers are not restricted to Christians. And importantly, the fact that they are officers of the Court does not prevent them, upon leaving the courtroom, from continuing to follow whatever faith they had when they entered.
And with all of this, I have yet to hear of a single Christian who avows that a court of law is a religion, or that it disavows Christianity, or that it "teaches" that Justice and Equality are not divine gifts. No one thinks twice about the fact that we are left to our own devices to contemplate for ourselves the nature and origin of the principles practiced and avowed within the Court. And the same goes for other highly ritualistic organizations, such as our Legislature.
Now I called the above "an analogy", but it's more than that. It's an exact representation of a lodge's relation to religion. The proceedings of the Court express the least common denominator of all of our society at large. You might say it is the common expression of our devotion to Justice.
Symbolical Masonry : "The prayer is in the Masonic ceremony because it must be in the Masonic life, and the important point here is not how we came to pray, but why we do pray; and the reason we do pray is that we cannot help it." For the same reason, we have scripture displayed. It's the same scripture that we would otherwise use in our various churches. But because we are of diverse religions (or denominations within a religion), we leave all matters of religious doctrine out of our proceedings. Instead, each brother carries his faith in his own heart. We refer to God by titles that are common among us, of which He has many, and which are not exclusive of any other titles He may have. What you see of religion in the lodge is not a teaching of doctrine... it is the common expression of our devotion to Brotherly Love.
Believing as we do that God is creator of all mankind, and that He would have us love our neighbors, and that this charge was never limited to those who share a country or a building or a doctrine, we gather for the purpose of promoting Brotherly Love.
For that is the purpose of the lodge. Brotherly Love brings us together for mutual support, the aid of those who are distressed, of our widows and orphans. Beyond that, we extend our charity to our communities; to fund hospitals and therapies and medical research through our appendant bodies like the Shrine and Scottish and York rites. The very word "charity" means "love". We do indeed concentrate on charitable acts, but it is not at all accurate to say that we "teach salvation through good works". Masonry does not teach that doing good works will bring you salvation... in fact, it is not our mission to teach salvation at all, as that is taught in church. For instance, it is the teaching of my Christian faith that leads to this syllogism: good works are the inevitable fruit of faith; every Mason is a man of faith; therefore Masons do good works. As with prayer, we do it because we cannot help it.
We encourage good works because it is always our aim to improve ourselves. And though we will never reach perfection, that is and should ever be our goal. I personally like having an unattainable goal. No matter how hard I try, no matter what I do, there is always more. My best efforts are always ahead of me. At the same time, knowing that my goal is unattainable reminds me that I will never achieve it on my own merits. As a Christian, the very attempt highlights for me the immeasurable gulf between that which I can achieve through my own efforts and that which I will nevertheless attain through Grace. My quest for perfection helps keep me humble before God.