Laying SBF at the feet of effective altruism is more than a little silly. It'd be similar to associating the Democratic National Party with Bernie Madoff, or Epstein with any of the universities and foundations he donated to.
One of the things criminals do to hide their activity, assuage their guilt, or put on a good show is associate with legitimate organizations. Social organizations typically don't and probably shouldn't do intrusive investigations into the lives and activities of their members sufficient to uncover their crimes.
When such organizations learn of any benefits accrued through the illegal activities of members, there are obviously moral and sometimes legal requirements to disassociate, disavow, and return ill-gotten funds.
Tegmark and Bostrom should be no means be tainted by association with EA. Their ideas and work on AI alignment and safety are excellent, and they ask the questions that should be answered as AI starts to reach human levels of competence and beyond.
EA tend to be a bunch of intellectual windbags, by and large, and overestimate their impact on the world at every level it's possible to do so. Just because they collectively gasped and claimed responsibility doesn't mean their interpretation has anything to do with reality.
The reality is SBF was a con man, and however complex his motivations and personality and psychological issues, whatever his ultimate intent, he willfully scammed a lot of money from a lot of people. EA might have been an influence, but SBF is a human with complex agency whose actions can't and shouldn't be reduced to membership or association with a community.
Going from "here's a set of good ideas about how to effectively give to charity, since we see a lot of corruption and inefficiency in charities" to "we have a moral duty to ensure that we only associate with good people" is how you go from a good idea to a pompous internet cult.
"We're not going to make it, are we? Humans, I mean." --John Connor