As a Gen X-er, I sit back and watch as the Baby Boomers and Millennials battle it out on the internet. And, to be honest, it's also the Gen Zs, some of whom think everyone over 40 is a Baby Boomer. Let's remember that (if we go by the years 1981-1996 for Millennials) the oldest Millennials are sneaking up on 40 themselves. Remember that the oldest Baby Boomers (1946-1964) are only 73. Which is what made this exchange with William Shatner (born 1931) so hilarious:

As a Star Trek fan, I'm already biased, but even if you're not one, this is pretty funny. 

But what if BillieE and Shatner worked together? Then it ceases to be a joke and becomes a serious problem.

You can say I'm too sensitive, but I also have no dog in this fight. I'm a Gen X-er (we should call ourselves the forgotten generation). But the Age Discrimination in Employment Act of 1967 (ADEA) prohibits discrimination against people 40 and over. What it doesn't do is prohibit discrimination against Millennials--until 2021, when they start turning 40. Federal law doesn't protect the under-40 crowd, although your state law might.

If your employees are using the "OK, Boomer" line on your older employees--including Gen X-ers and Silent Generations (what Shatner is), it can create a "hostile work environment." 

People often think this term means a place that is hostile, but it applies specifically to behavior that violates the law--such as age, race, or sex discrimination. Since the under-40 crowd isn't covered, Boomers calling Millennials "snowflakes" is hostile, but it doesn't create a hostile work environment. 

It's OK that that isn't logical--no one says the law ever is. 

But here's the thing: if you have an employee, of any age, dropping the "OK, Boomer" line against any employee who is over the age of 40, you have to take it seriously. You can't dismiss it as a harmless banter. Just the same way you wouldn't dismiss it if someone said, "OK, Mexican." It doesn't matter whether the employee is a Mexican or not, or whether the target of "OK Boomer" is a Baby Boomer or not. One time is a joke, but it can lead to patterns that create a hostile work environment, putting the company on the receiving end of a lawsuit.

So, you counsel that employee, and if it doesn't stop, you terminate the employee. You'd do the same for someone who continued to mock someone because of their race. 

I know there will be people saying, "You can't take a joke!" I can. What doesn't take jokes is the law. So, if you want to take this catchphrase into the office, it may be the last thing you say at work.

Instead, let's all be kind to each other. We all become old eventually, and the older generation thinks the younger one is stupid while the younger one thinks the older one ruined their lives. Yawn.