I had Max Tegmark as a professor when I was an undergrad. I loved him. He is a great physicist and educator, so it pains me greatly to say that he has gone off the deep end with his effective altruism stuff. His work through the Future of Life Institute should not be taken seriously. For anyone interested, I responded to Tegmark's concerns about AI and Effective Altruism in general on The Luddite when they first got a lot of media attention earlier this year.

I argue that EA is an unserious and self-serving philosophy, and the concern about AI is best understood as a bad faith and self-aggrandizing justification for capitalist control of technology. You can see that here. Other commenters are noting his opposition to open sourcing "dangerous technologies." This is the inevitable conclusion of a philosophy that, as discussed in the linked post, reifies existing power structures to decide how to do the most good within them. EA necessarily excludes radical change by focusing on measurable outcomes. It's a fundamentally conservative and patronizing philosophy, so it's no surprise when its conclusions end up agreeing with the people in charge.