I suppose the problem with the word "bitterness" is it may imply that our comments about the WTS are more "emotional" and a bit less "rational." That our perceptions have been clouded by the emotional reactions we've had from our *personal* experiences.
You know how it goes. There's a restaurant in town that most everyone loves. But you find one person who tells you that it's positively dreadful--and that they will NEVER go back. Perhaps they had a bad experience one time, and--despite it's relative rarety at this establishment--they will forever speak nastily of it. Anyone else's experience is irrelevant. So their experience has caused them to be bitter, and for that reason someone may consider their opinions as tainted.
And to a greater or lesser degree this can be true. There are probably a number of ex-JWs who know nothing about the 607 B.C.E. mistake, the pyramidology Russell utilized, the "fornication" with the United Nations, the history of protecting pedophiles, etc. They didn't like 'the way they were treated' a few times, and now they just speak angrily of the organization. For most of us though, any "bitterness" is accompanied by reams and reams of shocking discoveries about the WTS. Not just about certain "bad things" that have happened over the years. Not just about certain "mistakes" that have been made. But more importantly their "covering over" of these things--in a way that would get any *individual* within the organization disfellowshipped, keeping important information from those who have a right to it--and often quite viciously using their authority to manipulate the flock, willfully ruining people's lives to protect their empire.
To me? Right now, a bit over one year into my awakening, I'm just really happy that I finally figured it out. While it's true that I had certain personal experiences that were negative--they were far, far less so than the experiences many others have had. I can say with great confidence that the righteous indignation I feel toward the WTS is not because of any personal experiences, but instead from the awareness I now have of how deep their deception and manipulation reaches into the lives of human beings. The very human beings they purport to keep watch over. The ones they themselves emotionally threaten.
In my case, the negative experiences I had did not make me bitter--to the degree that I would misrepresent or exaggerate the truth about the WTS. They only gave me the permission (FINALLY) to give the organization an objective investigation.