Opposition to Indiana's Religious Freedom Restoration Act, which was signed into law by Indiana Governor Mike Pence last week, has been particularly strong among the tech and hobbyist sectors, and that opposition grew even louder thanks to a letter written by Apple CEO Tim Cook.

His Sunday op-ed, printed in The Washington Post on Sunday, didn't mince words, describing Indiana's new bill—and similar bills around the nation, including a few that have yet to be signed into law—as a "dangerous" means of enabling discrimination. He urged states considering similar laws to think again, pointing out how their signing "truly will hurt jobs, growth and economic vibrancy."

"These bills rationalize injustice by pretending to defend something many of us hold dear," Cook wrote. "They go against the very principles our nation was founded on, and they have the potential to undo decades of progress toward greater equality." Cook went on to describe his stringent religious upbringing: "I have great reverence for religious freedom. As a child, I was baptized in a Baptist church, and faith has always been an important part of my life. I was never taught, nor do I believe, that religion should be used as an excuse to discriminate."

Yelp CEO Jeremy Stoppelman went one step further in an open letter he penned last week by throwing down an ultimatum: where similar, discriminatory laws are passed, his company won't follow. "Yelp will make every effort to expand its corporate presence only in states that do not have these laws allowing for discrimination on the books," Stoppelman wrote in a letter that echoed the points he'd made to Arizona last year over similar legislation.

May's Indy Big Data Conference appears to be the first major Indiana tech event to suffer from the law's signing, as major companies like Oracle, EMC, and Cloudera have already pulled out in protest. The conference posted a response on Monday to call for the bill's "immediate correction." And as Re/code reported, travel site Gogobot has begun warning users who look up travel tips in Indiana about the law with a warning that states, "critics of this law say that it may legalize discrimination against travelers due to their sexual orientation."