Did Plato really say this?

I hope not, because neither of those are forms of knowledge. Knowledge is justified, true belief. An opinion is a conclusion based on belief (that hopefully is justified and true), and empathy is a capacity that can be exercised.

I guess it's true that opinions don't require accountability or understanding, but they can certainly carry both, and opinions have literally changed the world for the better. "All people should be equal under the law" is an opinion (not, notably, knowledge). "Consent should be required for sex" is an opinion. "Children should not be abused" is an opinion.

Empathy can be cognitive (I understand what you're thinking) or affective (I feel what you're feeling), and is necessary IMO for not just morality but relating to other human beings at all. It's not knowledge, however, and in some cases isn't even moral (manipulating someone, after all, requires understanding what they think and then using it against them).

And no, I don't think I'm nitpicking here. It's bizarre to try and rank forms of human knowledge in the first place. Knowledge is just knowledge. It's what you do with it that matters. And what you can do is form rational, informed opinions, and become better at empathizing. Both of these are immeasurably valuable in their own right-- neither is benefited by being redefined as "knowledge."