These employees are free to exercise their right to (not) work for whomever they want, but the certainty they express (as well as most commenters here) in their own self-righteousness seems misplaced to me. There's certainly a case to be made that a strong US military is in the world's best interest. In fact, I would wager that a majority of Americans (and a majority of citizens of democratic countries across the world) hold the belief expressed in the previous statement.

Given that society created the environment for these tech companies (and their employees) to acquire their skills and thrive, does not society have some moral/ethical lien on how those skills are applied?

Granted, as stated in the first sentence, I'm not in favor of compelling anyone to work for any purpose, let alone military ones. But to pretend such a lien doesn't exist strikes me as somewhat selfish/narrow-minded in its own right. For that reason, I think the ostensible certainty that these employees (and their abundant proponents here) have in their convictions seems a little naive to me.

There's also a real chance (though perhaps small) that an industry-wide refusal to cooperate with the US military could have disastrous consequences for the world, and that alone should give one pause before being so self-assured about such a decision. I agree that there is also a real chance (also perhaps small) that the US military could use the technology with disastrous consequences for the world, but--again--that makes this a difficult ethical conundrum, not the clear right/wrong moral issue as I often see it portrayed as in the industry.