Fischer probably didn't care much about Carlsen because he was really young at that time. Fischer didn't interact much with the media anyway, so we will never know. There were other child prodigies like Karjakin at that time too. Fischer might have frowned upon the computer influenced chess of this age, for all we know, but this is all speculation.
On the other side, I was surprised to find what Carlsen thought about Kramnik here --> http://susanpolgar.blogspot.in/2014/03/carlsen-kramnik-thinks-he-knows.html
i was just wondering.. Did fischer know carlsen? Did he watch the carlsen-kasparov match? What did he think about it? Did he pass any comments? What did kramnik think about it aswel as anand? Not forgeting karpov did he comment on his game and that of kasparov?