Actually every once in a while I kind of do this with a buddy of mine. We'd take random holds and partially bolt it on the wall, randomly spin in, stop the hold at some random position, and randomly tighten. Do the same with the other holds and when done, we try to figure out how to negotiate it, kind of like.. finding a brand new boulder problem outdoors and working out the beta :). Super fun.
That being said however, we only restrict ourselves to doing this on our own woodie, or when we're ahead of our setting cycle and just want something different to train/climb on in the gym - it's "extra" holds we put on the wall, and never part of our commercial setting cycle.
And I apologize for not answering your question earlier:
"Also, have you ever had to deal with people that just won't agree to your idea of the grade? Like people that just scream personal insults cause you don't think they were right in grading a route based on half the climb?"
Absolutely. That's part of the setting game and comes with the territory. You're NEVER going to make everyone happy. Even the best setters in the world still get bashed on by pro climbers on their sets and their grading. It may be your fault, or it may not, depending on your experience as a setter and your, and I say this lightly, "accuracy" of the grade. But what I find is that most people who have the audacity to consistently bash on setters and complain about grades have an ego the size of the wall they're climbing on. What they think is right, and very little will deter them from that mindset.
The best method of grading that I find is to get a consensus. After the set, leave the problem ungraded, and let people run it for a day or two and see what they say. 12 people can't be wrong against 1 egotistical climber.