I absolutely agree with your opinion of there being no other reasonable thing to do than to accept what happened and move on. It's easier said than done to most people though, and each individual has to grapple with the issue from his/her own unique circumstances, which means that there's a ton of homework to be done in order to get things right. Ultimately though, it is the correct thing to do, if for no other reason than it being the only thing you can do really, lest you become a neurotic, spiteful husk of a man, at least in comparison to who you could be.
I sufferred constant bullying and intense humiliation myself for years in my adolescence, and the scars are with me to this day. I've read a ton of books in order to better understand the science behind the psychology of the proposed treatments for victims of bullying, among many other conditions, so that I can apply the best methods to work on myself with. Cognitive Behavioral Therapy is of course the most recommended treatment, but it comes in many variations and sizes, and you really just have to try different approaches in order to find the one treatment that suits you and your goals best. Of the books I've read, I believe that the ones written by the norse psychololgist Dan Olweus and the swedish doctor Peter-Paul Heinemann have been the best in describing the science behind bullying; Dan Olweus in particular is still widely cited to this day. The inquiries conducted by Olweus found, in no uncertain terms, that most bullies bully for no particular reason other than that they can, and because it raises their social standing in the eyes of others. This is the part of your post that I wanted to quote and comment on. I'm very happy that you got into contact with your former bullies, made peace with them, and even received a reasonable explanation for their behavior, but I would think that these kinds of rational explanations — rational in the sense that it's understandable to some extent from your perspective as the victim — for bullying are not the norm.
I know that some of the most vicious bullies from back in my adolescence are living great lives, have a very high education (one is a general practitioner for fucks sake, and have a fantastic house and a beautiful wife and family), and that's just the way it is. I got in their crosshairs because it was fun for them to have a punching bag, and their assertiveness elevated their social status. It's a very bitter pill to swallow, but what else can you do than to accept it and move on? At the very least I've had a fantastic family to support me and guide me in the process. For as many evil, vile cunts there are in this world, there are also terrific people. There are also many other people who have gone through what you've gone through, and it's solacious and therapeutic to find common ground with these people. The fact that so many people find effective ways to cope with their traumatic past and accept it, is testament to there being something else going on with people like Dobson that makes them who they are. By this time, so many years after the supposed bullying (I read some post that said the he admitted to making some of it up?), he should at the very least have made some tiny progress with his past.