See the full post for more details on exceptions
"While we’re not bound by international human rights laws that countries have signed on to, we are a member of a global initiative that offers internet companies a framework for applying human rights principles to our platforms. We look for guidance in documents like Article 19 of the International Covenant on Civil and Political Rights (ICCPR), which set standards for when it’s appropriate to place restrictions on freedom of expression. ICCPR maintains that everyone has the right to freedom of expression — and restrictions on this right are only allowed when they are “provided by law and are necessary for: (a) the respect of the rights or reputations of others; (b) for the protection of national security or of the public order, or of public health or morals.”Hard Questions: Where Do We Draw The Line on Free Expression? -- Facebook Newsroom
The core concept here is whether a particular restriction of speech is necessary to prevent harm. Short of that, the ICCPR holds that speech should be allowed. This is the same test we use to draw the line on Facebook. After all, giving everyone a voice is a positive force in the world, increasing the diversity of ideas shared in public discourse. Whether it’s a peaceful protest in the streets, an op-ed in a newspaper or a post on social media, free expression is key to a thriving society. So, barring other factors — and there are several crucial ones that I’ll discuss — we lean toward free expression. It’s core to both who we are and why we exist."