Whether or not you should be requiring the consent of all people with similar DNA is the real question -- but given Americans' obsession with individual rights I don't see it changing. In their eyes, why shouldn't they be permitted to upload and share their own DNA?
So this isn’t about sharing a selfie, this is about sharing a group photo, where other people are partly out of frame, but you can still make out who they are. And if we stitch together enough photos, we can make out a lot of people, people who never even took a photo.
Although, some would be sharp to point out that in the case of a selfie most of your facial features are also not your own. So it’s mostly a question of where we draw the line as to what is personal and what is shared. But in the case of a murder, if we had an actual selfie of the killer at the scene, we would be able to solve the case fairly quickly using standard investigative methods.