Since it is generally impossible to end voluntary divisions without understanding what is driving them in the first place, perhaps you would be good enough to suggest just why the world of ME/CFS is, according to you, so extremely fragmented organisationally.
I don't think I have a perfect answer to this question, but here is the best one I have:
It is the difference between unconditional support and conditional support. Advocates for most other diseases offer unconditional support, but for ME/CFS the support is conditional. (I don't think the cause of this is a mystery: it is because of the bad things that have happened in the past.) To understand what I mean by unconditional vs. conditional support, consider the following story (which is a slightly fictionalized version of something which really happened, and just a few weeks ago):
Someone posted in the forum/blogosphere and said: "I represent group W, and we are working with politician X, to get Y million dollars allocated for ME/CFS research by the Z government agency. Will you help us?" The responses fell into three categories:
1. People who said "yes, I'd love to". This is unconditional support.
2. People who said "I need to know more before I make a decision on whether to help you. What sort of research will be funded? Will psychologists be able to get the money? Will the research be forced to use the definition that I like? Will the research be banned from using the definition that I don't like? etc." This is conditional support; the person is willing to help, but only in certain situations.
3. People who said "I will not help because group W or politician X or government agency Z has done bad things in the past, and I will not help them with this project now." That is a different form of conditional support; it is based on the purity of the actors rather than the desirability of the actions.
In the world of ME/CFS, the most common response was number 2. The second most common was 3 and 1 was the least common, in general, according to my memory. When similar questions have been asked in forums for other diseases (including those with unknown causes), the answer is almost always 1, with a small (or tiny) group of 2 and 3. The difference is striking. (And I want to say again: the reason for this is well known, it is the history of bad research and bad management by government agencies and so on.)
I think this attitude is critical to creating the organization fragmentation in ME/CFS advocacy. If most people answer give answer 1 when asked about more money for research (a critical need), there is simply nothing to argue about. The group of people can't fragment, because they all agree on more money, and everything else is secondary. On the other hand, the moment you start thinking in terms of 2 and 3, lots of fragmentation because possible (even easy). Some people will argue over disease definitions or terminology, others over most promising cures, others over definitions of improvement. The list is potentially endless, and every question has the ability to divide every group in half. The group that insists on ICC could be cut in half by a immune vs. mold argument. The ICC-mold group could be cut in half by the ME vs SEID naming argument, the ICC-mold-ME camp could be divided by the allow psychologists vs. ban them argument, and so on.
Additionally (and maybe even more destructive) conditional support has the practical effect of gutting government funding. Such diseases can almost never get an "special funding" allocations. In real life, there are lots of people who want lower taxes. To get lower taxes they are against almost all government spending. So any politician who wants to spend money, has a large group of people who are against that. So, they will only work for a special allocation of research money, if (a) they really believe in it very strongly and personally or (b) they think they will get support from the people they help enough to offset the people who will be against it.
If a politician says "I'm going to work for a special $5 million Parkinson's allocation the Parkinson's advocates will all give answer #1, and the politician will get support. But if they announce a $5 million ME/CFS allocation, they will get a mix of answers #2, #3, and #1, and the politician will get much less support, and might even get controversy for their efforts (and this from the people they think they are helping!) The result is that the politicians will support more funding for Parkinson's Disease, and the other diseases with similar advocate attitudes, and will not work for more funding for ME/CFS.
Also remember, that government funding happens before specific research projects are chosen. You get the $5 million, and then you figure out what research projects will get it. So in answer #2, when the person asks "What is going to be funded?" the answer is usually "We don't know", and then the person does not support it, because they are worried about it, and the money never materializes. The #1 unconditional supporters don't have that problem, because they never even ask the second question. They just support more money.
Joshua Levy