"he asked if "that's socially irresponsible" some poeple might say "yeah, but so what". That's fine if you want to be that way, but at least ask yourself if you really believe that."
No I don't really believe that. I don't believe that protecting myself is "socially irresponsible" to begin with.
"...but the point is that it's somewhat selfish to train to defend yourself and nothing else at all."
There is no such thing as "yourself and nothing else at all". I do not exist in a vacuum. When I train to defend my life I train to defend everything that is dear to me. I train to defend my freedom, my family, my right to act of my own volition etc. etc., and if I so choose, to defend a stranger on the street. Yes this may be selfish. So what.
"The fact of the matter is that at it's core Aikido is a peaceful art, where one strives to NOT hurt the attacker in this case, as the highest goal. ....Aikido goes one further and says you should help them. What I'm trying to get at is does this make it a "selfish" art in the sense that sometimes it may be better for society to do something other than help the aggressor, or is there some other thing that I'm missing entirely?"
I don't know that to "not hurt the aggressor" is the highest goal of aikido. As I understand it, the goal of aikido is to restore harmony. Whether or not the aggressor gets hurt is, in theory, up to them. And maybe I am missing something but where does it say that I must help the aggressor (other than to help them see that using force against others is wrong)?