We didn't include the antiblocker, as it felt too specific in purpose. There's a way to have the same effect, although it takes two nodes: hook a flipflop node up to the blocker, then flip the flipflop in the editor. As long as the flipflop is inaccessible to packets, the blocker will act like an antiblocker.
The antiblocker was a post-release addition to the editor at the request of Kongregate player Enthernalcz (who I'm guessing is now @Enthernal on the forums!). The original Exploit didn't have flipflops, so the antiblocker was a way to clear loop memory and perhaps make the Exploit puzzle system Turing-complete. With the addition of flipflops, it's hopefully less necessary.