How does Asagai define idealists and realists? Which group does he prefer to be associated with?

From the text:

It isn’t a circle—it is simply a long line—as in geometry, you know, one that reaches into infinity. And because we cannot see the end—we also cannot see how it changes. And it is very odd that those who see the changes—who dream, who will not give up—are called idealists…and those who see only the circle we call them the “realists”!

Asagai implies he is an idealist.