It's hard not to rewrite someone's goals while educating them, because one of our inborn drives is to gain the respect and approval of people around us, and if that means overwriting some of our goals, well that's a small price to pay as far as that part of our brain is concerned. For example, I stayed for about a week at the SIAI house a few years ago when attending the decision theory workshop, and my values shift in obvious ways just by being surrounded by more altruistic people and talking with them. (The effect largely dissipated after I left, but not completely.)

I think it's not an ethical imperative unless you're unusually altruistic.

Presumably the people they selected for the rationality mini-camp were already more altruistic than average, and the camp itself pushed some of them to the "unusually altruistic" level. Why should SIAI people have qualms about this (other than possible bad PR)?