Though I was not baptized (so my struggle may be different from those who were), I was raised in "the truth." In fact, my mother was pregnant with me when she was baptized. I spent the first 18, 19 years of my life being told that everything about me was wrong for my refusal to be a joiner. It takes a toll on the spirit to be told that you are a bad person, defective. So I am quite bitter because I was denied unconditional love as a child and very little self-value was instilled me.
In fact I have recently moved back in with my parents. I believe they are geniunely disappointed that I am not shaking my fists with rage at the world because I've had a hard time finding a new job, and this should have proven to me that the world is full of evil and to store treasures only with Jehovah, blah, blah. The first week I was here my mother asked if I was attending the meeting that night. I said no. (I have not been to a Kingdom Hall in over 10 years. So it's not like I have ever sent a mixed signal about my choice.) She did not speak to me for three days. The rejection still burns.
But with that said, I don't think it's fair to lump everyone together as all our histories and motivations will vary. Also I don't think bitterness is an unreasonable emotion when one looks at all that was lost and wasted. But I do think it's terrible to remain bitter forever. While I haven't worked through the bitterness phase, I don't want to be in this place forever.