I don't see why this is necessarily true, unless you treat "altruism toward humanity" as a terminal goal.

Well, yes. I think that's the point. I certainly don't only value other humans for the way that they interest me - If that were so, I probably wouldn't care about most of them at all. Humanity is a terminall value to me - or, more generally, the existence and experiences of happy, engaged, thinking sentient beings. Humans qualify, regardless of whether or not uploads exist (and, of course, also qualify.