Cho did what he was taught, No?
In public schools today students are taught that everyone should follow their heart. Cho did that. You're to be true to yourself. Cho was. You're to respect the opinions and beliefs of others. Cho believed that respect should also be afforded to him. You're taught that we're all here by happenstance and there's no absolute, unchanging and universal truth by which man should govern his life. In Cho's mind there was no binding moral code to violate, perhaps just some some nuisance laws prohibiting murder.