Someone could be trying to impersonate the site and you should not continue.
Websites prove their identity via certificates. Firefox does not trust www.hrw.org because its certificate issuer is unknown, the certificate is self-signed, or the server is not sending the correct intermediate certificates.
I went to the page, it's blocked by the office network (as Advocacy Organizations), the warning was put there because the web filtering uses a certificate with a different name from the web site.
Or are you talking about the Great Firewall, which unsurprisingly appears to be blocking the Human Rights Watch website:
http://www.chinafirewalltest.com/?siteurl=https%3A%2F%2Fwww....
https://viewdns.info/chinesefirewall/?domain=www.hrw.org