What do you think about Sasuke? Good or bad person?
Sasuke is basically a very pure person who doesn't think about whether what he does is good or bad. He just does what he wants to do, which causes trouble for others. He's very self-centered, only concerned with himself. Some people might think what he's doing is good, like avenging his parents or trying to realize his brother's ideals. But he is troubling others in his pursuits, so that aspect is bad. So it's hard to say with clarity, but it's all about whether it's right or wrong to be so self-centered with your goals. I'd say he's not good or bad, he's just pure.
Of course, the parallels only exists at a very basic level; Chihaya obviously does not need to avenge anyone or otherwise kill to realise any of her ideals (and I don't think she would deliberately hurt anyone in order to do so). But at the same time, she is troubling others in her pursuits, so like Kishimoto says, it's about whether it's right or wrong to be so self-centered with your goals. (Though here too, I'd say that Chihaya is less self-centered than Sasuke.) So I think that the word he uses is fitting: a good descriptor for Chihaya is 'pure'.