you don't block 2000 servers distributed over the Planet
Discussion
It's ~2000 ip addresses that make up the exit nodes. The file is around 16kb and it's updated every hour. It's incredibly easy to blacklist those ip addresses from accessing your site. Don't believe me? Try accessing the Campspot website through the Tor network.
oh a sw block is easy but traffic can be route throu a VPN. i thought youmean physical take out