I don't know about this whole proxy thing. It kind of feels like if I were to express sympathy for a couple that confided to me that they were unable to have a child and they took my sympathy as a prompt to suggest, "Well, if you feel sorry, are you willing to be our surrogate?" and when I decline, them demanding examples of times when I actually showed real sympathy towards people, because I clearly am an unsympathetic person if I'm not willing to have their baby.
I just don't have that kind of relationship to most people that would make me feel comfortable expressing culpability for something that feels very separate from me. I can offer sympathy. I can offer suggestions for how to cope with the person. I can offer possible thought patterns the other person might have. But it just feels oddly inappropriate to my relationship with a relative stranger to actually apologize personally for something that someone (who doesn't even act in a way I identify with 100%) did.
Again, this is an extreme example, but it is meant to illustrate how out of nowhere it feels to be requested to either explain or apologize for another person's behaviour as if I were the person who offended in the first place. I really do want to understand what in your thought process would allow you to not feel weird about it.