Everyone pushes on a falling fence, and in this case, the falling fence is the aforementioned programmer. It's almost too easy to blame him here, IMO.
Playing devil's advocate, why wouldn't he (in this economy), only worry about focusing on his larger clients? The work he does for other larger clients is quite likely, (a) steady, (b) uncontested, (c) reoccuring. I've been in many similar circumstances where my corporate masters have told me more or less the exact same thing in even more blunt and crass terms, and I've been "the bad guy" for relaying that to my customers, who I felt had a right to know why I'm not calling them back.
So, it seems to me, his problem was perhaps not what he was doing as much as the fact that he was a bit too honest or blunt. In the whole grand scheme of IT professionals, being too honest or too blunt is a devil I can live with. Too many other "professionals" are trained to say "yes" to everything you say you want, and then play all sorts of games later on down the road when the rubber meets the road.
If you really need a Drupal, Plone, or (insert whatever CMS you might use) programmer, I would strongly suggest being more proactive about getting some alternate resources. For example, try putting up some ads in CraigsList or possibly putting up a request for professional services on one of the listservs or forum boards. Explain your situation -- services requested, work you couldn't get your previous programmer to do, budget, etc. -- and maybe someone else will bite. I'd recommend being honest about what you did not like about the previous guy in the hopes of finding someone who is a bit more compatible with your NGO's special needs.
Also, I would take tclaremont's advice and make sure that you have a clean backup of everything. Diplomacy is saying "Nice doggie while picking up a stick." Or, as Ronald Reagan would often say to Mikhail Gorbachev, "Доверяй, но проверяй." (Trust, but verify).