“I don’t think the attitude of employees of Google is representative of Silicon Valley,” said Nick Beim, a partner at Venrock who invests in artificial-intelligence startups. “I think there are a lot of startups that see [work for the U.S. military] as an important form of public service, as well as a business, and are motivated by the broader mission of saving lives.” As companies like Google step back in some ways, others will step up, Mr. Beim added.