Obviously you have a lot of options in front of you but if I were you I'd take the following route:
- Sign the PIP and get on a plan of action to improve whatever it is they say you have to improve.
- Start looking for another job immediately. Do not pass Go. Do not collect $200 (I mean, literally collect your paycheck but that's besides the point).
PIPs are generally given out for two reasons: one, to actually try and get a flawed but otherwise useful employee a path to improve themselves as an alternative to firing them, and two, a way to lay the groundwork to fire an employee who might otherwise be tough to let go, perhaps because the company itself doesn't like to fire people, or because the employee has friends placed highly in the company, and so on. I get the sense that your situation is in the latter portion, as it sounds like this boss with a personal grudge would have fired you outright if he really is that mean.
Even if it is the first one, it's often the case that having a PIP on your record at a company means that you are never going to be looked upon as a candidate for higher or lateral positions, or if you are you'll have to wait it out for several years. The world is too large for this IMO. Additionally, if it is the first one then you've seriously misread your boss's attitude towards you and it's pretty likely that you've done something else you haven't told us to hurt things between you. I guess if you feel up to it, you can talk it out with them, but I would remain calm about that and expect the worst, given you're posting here already doing so.
So look upon this as your opportunity to make the exit happen on your terms. I mean, don't do anything that will burn bridges amongst the people you've cultivated relationships with there by destroying company property or that kind of thing, but find another job, get another job, and kiss this one goodbye. Feel free to follow the PIP as well - no point in getting fired before you can quit - but you need to read the writing on the wall here, and the writing on the wall says you don't have a lot of time left at this place whether you like it or not.