article by Hope King via money.cnn.com

Mark Zuckerberg has always encouraged Facebook employees to think for themselves, but one issue is trying his patience.

People have been crossing out “black lives matter” on the walls of Facebook‘s headquarters and writing “all lives matter.”

The founder and CEO addressed the issue at a company-wide Q&A session last week. But it didn’t stop. Zuckerberg wrote a strongly worded memo to employees earlier this week about “several recent instances.”

In his note, the Facebook (FB, Tech30) CEO seemed frustrated by the fact that the act has continued, despite making it clear in the past that it was “unacceptable.”

“I was already very disappointed by this disrespectful behavior before,” Zuckerberg wrote. “But after my communication I now consider this malicious as well …This has been a deeply hurtful and tiresome experience for the black community and really…