Why God Is Small and Petty.
Read the bible. Then pick up any text describing the workings of a star say, or the mysteries surrounding quantum physics. The god of the Israelites just seems ignorant, weak, and irrelevant when compared the these wonders.
I see no reason to list religion's failings; I think they are obvious. But one insight I would like to share, as it is the primary reason I am so irritated by religious beliefs. Religion must always look backwards for explanations or inspiration. The single most revolting idea I know of is this lunacy of original sin. And what was the original sin? Why, reaching for knowledge of course. To its very core, religion fears new ideas; scoffs at the results of experiment and stifles the best qualities of the human intellect. Science is of the opposite charge. At its best, Science rewards those who quest for knowledge; lauds the arrival of competent new ideas and rigorously insists on verifying ideas with data.
Of course, Science has its dark side too. There is no question, that in many areas, our scientific abilities have far outpaced our ability to apply them responsibly. With global warming unchecked and the virtual guarantee of some sort of nuclear conflict in the future, no doubt this lack of responsibility will be felt even more acutely. Still though, a lot of these issues could be resolved if people stopped thinking religiously. Sure the tools of destruction are technological, but the motivations are still the same age old religious ones. Again, if you read the bible, all those cats were ever about was themselves, their families, and in a few cases their "people." None of these guys cared one bit how many were slaughtered, or what harm befell the environment around them, as long as their "godly" goals were accomplished.