SI is a very narrowly focused institute. If you don't buy the whole argument, there's very little reason to donate. I'm not sure SI should dissolve, I think they can reform. It's pretty obvious from their output that SI is essentially a machine ethics think tank. The obvious path to reform is greater pluralism and greater relevance to current debate. SI could focus on being the premiere machine ethics think tank, get involved in current ethical debates around the uses of AI, develop a more flexible ethical framework, and keep the Friendliness and Intelligence Explosion stuff as one possibility among many. This might allow them to grow and gain more resources (i.e., from the government, from military robotics companies wanting to appear responsible, etc), which would be a positive outcome for everyone. It'd also make it easier to donate, since instead of having to believe a narrow set of rather difficult to evaluate propositions, you'd simply have to value encouraging ethical debate around AI.