The dangling cigarette

As part of a discussion about Unitarian Universalism, a friend of many years told me recently that

It seems to me that religion implies by definition an assumption of the existence of a supreme being (or beings). The principles listed on the Unitarian Universalist website seem to be moral principles. I do not disagree with them but they are not "religious principles," because they are not based on religion. You are quite right in questioning their basis and the Unitarian Universalists' apparently exclusive reliance on the Jewish/Christian tradition. The reality is that in some sense the various world religions hold to these general principles.
    I disagree, though, with the view of your Muslim friends that Islam is "more about love and mercy than about killing infidels." Contrast the practice of Christ and his disciples to that of Mohammed and his disciples.
    If one concludes that God exists, the essential argument for Christianity is that no other religion or person has established standards for human behavior which approach the idea of goodness embodied in its concept of God. Certainly not Islam, which promises a paradise with delectable virgins for those martyred in their efforts to fight the infidel (you and me).

I agree with my friend about Islam, despite what a few justifiably defensive Muslims have told me. They may think that Islam is "more about love and justice than about killing infidels," but it seems to me (from my partial reading of the Qur'an) that it's "about love and justice as well as about killing infidels," with the relative numbers of constructive and destructive passages to be determined by objective textual analysis (by anyone who thinks it's worth the trouble).
    Rudolf Otto, in his 1923 book, The Idea of the Holy (which was assigned for a religion course I took at Yale), argued as my friend does that Christianity is the best religion. I observe, though, that each adherent argues the same about his own religion, Muslims insistently about Islam, for example—however wrongheaded those indoctrinated into Christianity might judge that.

This parochialism is one of the many indicators I have for writing religion off altogether. If God were what religions claim, then it seems to me that they'd have all "come together by now and love one another" (to paraphrase a lyric inspired by the Beatles). But it's obvious that religions are wishful enterprises, culture-bound, maddeningly tenacious in their hold over adherents.
    I ran across an image this morning in Philip Roth's 2008 novel, Indignation, that seems an apt symbol for people's being in thrall to their religion:

...at age fifty, after enjoying a lifetime of robust good health, this sturdy little man [the narrator's father] began to develop the persistent racking cough that, troubling as it was to my mother, did not stop him from keeping a lit cigarette in the corner of his mouth all day long. [emphasis mine; p. 3]

    Religion to its adherents seems to me to be like that lit cigarette to the narrator's father. What is religion's grip on people? Not even the unanswerable sociological argument (put by Bertrand Russell in Why I Am Not a Christian) that if a Christian had been raised by Muslims he'd be a Muslim (and a Muslim raised by Christians would be a Christian) can shake a Christian (or a Muslim) from his religion. Does the addiction to religion involve a virus that incapacitates rationality?