It's a fuck off comment because the manager asked an open-ended question and tweeter bluntly retorted that retaliation is illegal. The manager could be ascertaining the awareness and intent behind stirring up this substantial turmoil. It would be polite to give the manager the benefit of doubt until threats are actually made.
It would be polite for the manager not to allude to threats which would be unlawful to make outright. Where else do you see something like "Don't you know what could happen?" going in a situation like that?
And let's be clear here. There is absolutely no downside to the sharing of salary information from the employee's perspective, and absolutely no upside to same from the perspective of management. So when it comes to hauling the employee into a private meeting with higher-ups, who are already outright declaring their displeasure with the situation, I think the "benefit of the doubt" boat has sailed.
I can imagine a number of downsides to publishing pay rates. Not every workplace is a beacon of maturity and comfortable upper-middle-class wages. Some offices have politics, gossip, and troublemakers.
Immediately employees would be calling meetings with their manager to hear the justifications for pay rates they felt were unfair. This could repeat with each new hire, promotion, raise, bonus, and change in responsibilities. This generates wasted time and increased turnover. My wife's design company would virtually grind to a halt for a few days. Even after everybody is placated with their pay rate, each doling out project assignments would be a new opportunity for friction over who deserves to do what. Then let's consider accusations of sexism, racism, ageism. The number of discrimination lawsuits would likely be non-zero. There are also social introverts who don't want to turn half of their co-worker interactions into awkward conversations.
So once profitable workplaces that kept everybody moderately polite and happy could face several obstacles.
Handing out raises wouldn't solve all of these problems either. I'll admit some worker bees would probably get paid a little more.
> absolutely no upside to same from the perspective of management
Are you asserting that 95%+ of companies in the US have, and sometimes enforce, a policy that actively hurts them? I know companies do stupid shit from time to time, but you are basically saying salary confidentiality policies are some sort of mass MBA psychosis. After all, if there is "absolutely no upside" to management, why do we need labor laws to prohibit these policies in the first place?
Edit: So, I totally mis-parsed that statement. I thought you were stating there was no upside to management prohibiting salary discussions.