I didn't mean to start religious discussion, rather used this term as in writings of Mark Weber (value of hard work etc.). This is more about set of principles that shaped Western and American societies, not really being related to religion anymore.
Alas, it's still related enough to religion to easily lead to religious flamewars on the internet. The burden is on the commenter to pack the point in less flammable packaging. "Protestant mentality" is too generic a phrase not to have religious associations for many readers. If you said "Protestant work ethic" that would have been better, and if you had made it clear that you were referencing Weber, there would be no problem. Far fewer internet users are likely to start a flamewar against Weber.
dang, please try to read charitably into the comments you choose to moderate. The concept of Protestant work ethic in the US is centuries old and is effectively divorced from any religious associations it might have had in the 1600's.
It's not centuries old, but comes from Max Weber's surprisingly readable and brilliant book on the topic. But from a moderation perspective we have to look at effects, not intent. If you lead with a comment like that, the odds of somebody getting triggered—for whatever reason—and taking the thread into flamewar go way up. This is not a deep or very interesting point, it's just basic fire prevention.