상처 주는 이도 왜 그런 걸로 상처 입냐고 하는데 (not a full sentence) = [상처(를) 수는 이(사람)]도 {왜 그런 것으로 상처(를) 입냐고} 하는데, ... = [The one that hurts (me / you)] even says {why (I / you) feel hurt from such things}, (and / but ...) * 이 means 사람. * 상처를 주다 (inflict hurt), 상처를 입다/받다 (feel hurt). It can sound vague and unclear because it's not mention the object of the verb and the nature of the hurt. It is talking about some people hurting someone and not feeling sensitive enough to understand the fact that they are are hurting them and instead asking why the other person/people feels hurt with such things.