Change is not growth. Change can cause growth, but just because you've 'changed' does not automatically equate to growth. If you are still doing hurtful things, just now to other people, then you haven't grown, you've only changed.
Taking responsibility for your actions doesn't mean making new excuses for past behavior. It means owning up to those actions. It's saying "I did that" and not giving excuses or justification. It certainly doesn't mean that to make yourself feel better about things, you trivialize what happened. If it wasn't trivial to you when you did it, then accept your role and move on to new ways to conduct yourself if the old behavior no longer fits the way you want to act now. It's only growth if you really have evolved.
Remember, I was there too.