Why not just use a pre 1.8 build? Well Spigot is being updated not just for the protocol hack. There are updates that involve 1.7.10 version's as well.
Why would you block specific protocols? Well 1.8 brings a few annoying changes: The tablist and NPC/Boss names that appear/disappear when not looking at it.
The config default works to block 1.8 clients. In the future you can edit the config to allow/disallow specific protocols.
If you want to bypass the block give the permission:Code (Text):# List of all blocked protocols
# Kick message
message: '&cPlease use version 1.7'