The culture war over gay rights has entered the impersonal world of e-commerce.

A handful of advocates, armed with nothing more than their keyboards, have put many of the country’s largest retailers, including Apple, Microsoft, Netflix and Wal-Mart, on the spot over their indirect and, until recently, unnoticed roles in funneling money to Christian groups that are vocal in opposing homosexuality.

The advocates are demanding that the retailers end their association with an Internet marketer that gets a commission from the retailers for each online customer it gives them. It is a routine arrangement on hundreds of e-commerce sites, but with a twist here: a share of the commission that retailers pay is donated to a Christian charity of the buyer’s choice, from a list that includes prominent conservative evangelical groups like the Family Research Council and Focus on the Family.

The marketer and the Christian groups are fighting back, saying that the hundred or so companies that have dropped the marketer were misled and that the charities are being slandered for their religious beliefs.

The national battle was ignited in July by Stuart Wilber, a 73-year-old gay man in Seattle. He was astonished, he said, when he learned that people who bought Microsoft products through a Christian-oriented Internet marketer known as Charity Giveback Group, or CGBG, could channel a donation to evangelical organizations that call homosexual behavior a threat to the moral and social fabric.