If you know someone disapproves of a behavior, would you ever tell them you are engaging in that behavior?

Once I told a friend that I had to protect myself, so I wasn’t going to tell her about something I was doing that I knew she strongly disapproved of. She said that there is a clear distinction between voicing a different view point, and actually attacking someone for theirs.

I have to say I don’t grok this. To make an extreme example, if you knew a friend didn’t approve of murder (and who does?), would you tell them about a murder you’d committed (assuming there are no issues of accessories and other legal things that would get your friend into trouble if you tell them)?

Wouldn’t it be reasonable to expect the friend to think worse of you if you tell them? Maybe even to stop liking you? Or is it reasonable to expect them to compartmentalize things: I don’t like what you do, but I still like you.

Is that possible? How can you separate a person’s action from the person? What do you think? Examples would be very helpful in illustrating your thoughts on this issue.