There's no such thing as religion. No such thing (in a religious sense) as Judaism, Christianity or Islam. No such thing as Buddhism, Hinduism, Jainism, Mormonism, or even (the Pope notwithstanding) Roman Catholicism. To be absolutely honest, there's no such thing as atheism either. As Sam Harris puts it, "Atheism is nothing more than the noises reasonable people make when in the presence of religious dogma."
None of these isms are actually about any thing. There is no "objective" way to discuss any of these isms because there is no object to discuss. Even sports fans—as Jerry Seinfeld so eloquently puts it—have at least the shirts to root for; religion doesn't even have the shirts. Because that's what religion is: When you take away everything, even the shirts, what you have left is religion.
Of course, there is much real philosophy, especially ethical philosophy, that gets thrown in the big box marked "religion". But calling a tail a leg doesn't make it one, and calling an ethical philosophy a religion doesn't make it one either. It's easy to make the distinction: If the idea makes sense—even if it just makes enough sense to be wrong instead of meaningless—when you take "God" (or whatever label the religion puts on its incoherent mystical mumbo jumbo) out of it, then it's not religion.
The same is true of culture and tradition. An atheist Jew can participate in a Seder. Millions of Americans can celebrate Christmas without the slightest connection to Christianity. I myself know the lyrics, melodies and harmonies to a score of Christmas carols and sing them in December without a trace of irony or hypocrisy—it's how I grew up, a connection to my own childhood and family. Anyone can admire the great works of art, literature, architecture and philosophy without believing for a second that a cathedral is magnificent because it honors "God". Again: Take out "God" and leave in the connection to our families, our fellow human beings, our ancestors and our common humanity, and if there's anything left it's culture; if there's nothing left, it's religion.
When you have nothing left but empty words, devoid of meaning, then you have religion.