I read somewhere that converts to a new religion, as a general observation, never give up their former religion in its entirety. Their new religion, it seems, is just the old one minus what they didn't like about it. I tend to agree with this. With regard to Western Buddhists, their former Christian values seem at some level present especially when it comes to being socially engaged, performing charitable deeds, etc. This also includes the rejection of karma and rebirth to a limited degree. What they have mainly opted to jettison is the idea of a Creator God and that Jesus is the only way. I might also add, they’ve dumped the Nicene Creed.
Generally, I would say there is something wrong with this. But history speaks to us differently on this subject. A new religion is mainly made up of members of another religion who find the new religion more adequate for various reasons. In the example of Buddhism, many of its converts were from other religions. Upali, for example, before he converted to Buddhism was a Jain. The Japanese scholar Iwamoto Yutaka claims that over 50 percent of the Buddha’s disciples were of Brahmanic origin. In light of this, no one can imagine that a monk or a nun, when the Buddha taught, had purged themselves of Brahmanism. In fact, much of the Pali Buddhist canon doesn’t have anything bad to say about Brahmanism. Not too long ago, the Buddhist scholar, Christian Lindtner argued that Buddhism should be seen as ‘reformed Brahmanism’.
Turning back to Christianity, we should also remember that during its formative stage when the apostle Paul was still composing his Epistles, many of the Christians were once Pagans. How much “Paganism” is embedded in Christianity is a subject that has seen a lot of books and papers published. Certainly both Plato and Aristotle have to be counted as Pagans who greatly influenced the early Church. In fact, when we take away from Christianity all of the influences of Paganism, a theology library would shrink down to a few books.
It is not a bad thing to have been a Christian who decides to convert to Buddhism; who brings with them some Christian values to the altar of Buddhism. Buddhism, I think, is designed to take additions. However, it will not survive for long with those in the darkness of their own ignorance who want to toss out the main elements of Buddhism such as karma and rebirth or purge from its teachings the transcendent in an attempt to secularize it; making it the good little house boy of the physical sciences.