Namecoin would make the resolution of tobacco.bit to the correct server IP. If an ISP blocks a website he normally blocks the domain, not the corresponding IP. Else, e.g. for the case that the website uses the widely used DDOS protection of CloudFlare, the ISP would block the IP of CloudFlare and thus a bundle of other not affected websites. Further multiple websites can be hosted at the same IP. Also a server can have redundant IPs for load distribution and failover DNS, what might even change dynamically. Therefore IP blocking is hardly used. And even if domain name and/or IP blocking would be used you could surf over a proxy server/VPN or even use the Tor browser with a cascade of several proxies (what will, however, slow down your internet speed drastically). The ISP has no control over your VPN. But this is nothing Namecoin would have to resolve. Also there doesn't and didn't exist any browser plugins resolving also ICANN domains as every browser resolves it natively. There are several plugins outside what don't work anymore after the OpenNIC project threw out Namecoin as noted in this already linked topic. Our discussion begins to go around in circles.