That could only be the result of something being off/bad in your front-end or steering system. Your steering stabilizer has nothing to do with whether or not it is "terrifying" at speeds over 70 kmh. Your steering should be fine and stable with or without a steering stabilizer. Again, as described above and how it is often described, its job is really not to "stabilize" the steering.
I have driven my TJ several times without a stabilizer and frankly, I couldn't tell it was gone and even kind of forgot it was gone.