You didn't tell if, when trying to visit rt.com, you arrive at a page with a message about the blocking, or simply a blank page, or you see the rt.com site. In the latter case, it would indeed be a MITM attack by way of DNS hijacking and a proxy. In the former cases, it's not MITM because you never see the content you wanted to see.
I see the chrome invalid cert page (inline in my original post)
sputnik news does an HTTP redirect to an ISP page about censorship
If the DNS server of your local ISP maps rt.com into an IP address that it controls but for which the server has a certificate for a different domain, i.e. upc.biz, there is a conflict: your browser still has rt.com in the address bar (it is not a http redirect) but it sees a certificate for upc.biz, so it reports a certificate error.