Although now that I think about it, I wonder what buddism poisoned....
I will start with one of Buddism's most harmful teachings, that enlightenment makes you morally infallible, like the pope, but more so. Even the otherwise sensible James Austin perpetuates this insidious notion.
'Wrong' actions won't arise," he writes, "when a brain continues truly to express the self-nature intrinsic to its [transcendent] experiences." Buddhists infected with this belief can easily excuse their teachers' abusive acts as hallmarks of a "crazy wisdom" that the unenlightened cannot fathom.
But what troubles me most about Buddhism is its implication that detachment from ordinary life is the surest route to salvation. Buddha's first step toward enlightenment was his abandonment of his wife and child, and Buddhism (like Catholicism) still exalts male monasticism as the epitome of spirituality. It seems legitimate to ask whether a path that turns away from aspects of life as essential as sexuality and parenthood is truly spiritual. From this perspective, the very concept of enlightenment begins to look anti-spiritual: It suggests that life is a problem that can be solved, a cul-de-sac that can be, and should be, escaped.
Although Buddhism seems so different from religions like Christianity and Islam that it doesn't look like it should be in the same category, it still shares with other religions a very basic element: a belief that the universe is in some fashion set up for our sake -- or at least set up in a manner conducive to our needs. In Christianity this is more obvious with the belief in a a god that supposedly created the universe for our benefit. In Buddhism, it is expressed in the belief that there are cosmic laws that exist solely to process our "karma" and make it possible for us to "advance" in some fashion.
This is one of the most fundamental problems with religions -- pretty much all religions. Although it's more of a problem in some and less of a problem in others, it's still a fairly consistent problem that people are falsely taught that there is something in or above the universe that has picked them out for special protection and consideration. Our existence is a product of luck, not divine intervention, and any improvements we achieve will be due to our own hard work, not cosmic process or karma.