(Reuters) - Apple Inc's Tim Cook, one of the most prominent openly gay American CEOs, has joined fellow tech industry chiefs in decrying a controversial Indiana law that opponents say could allow companies to deny services to gay people. Cook, who publicly declared his sexual orientation last year, joined other tech chief executives, including Salesforce.com Inc's Marc Benioff, in blasting the Religious Freedom Restoration Act, which could let business and individuals turn away customers by citing "religious freedom." Indiana Governor Mike Pence signed the controversial bill into law on Thursday.