After the brutal terrorist attacks on the French satirical newspaper Charlie Hebdo this week, Facebook CEO Mark Zuckerberg posted on the site and pledged its dedication to free speech.

“Facebook has always been a place where people across the world share their views and ideas,” Zuckerberg wrote. “As I reflect on yesterday’s attack and my own experience with extremism, this is what we all need to reject — a group of extremists trying to silence the voices and opinions of everyone else around the world. I won’t let that happen on Facebook. I’m committed to building a service where you can speak freely without fear of violence.”

Facebook, which adheres to the laws of whatever country it operates in, has come in for harsh criticism for acting as a censorship tool for repressive governments like Russia. (For instance, Facebook reportedly took down an events page organizing a support rally for Russian political dissident Aleksei Navalny.) There have been other reports of Facebook honoring  content removal requests from oppressive regimes.

The ease with which anyone, virtually anywhere in the world, can access Facebook undoubtedly makes it a valuable tool to promote free speech. However, Facebook’s own practices too often undermine that lofty objective. Even if Facebook won’t let itself be used as a platform for extremists, it can muffle speech all on its own.