I think your warning is justified and well-written, but unfortunately I don't think many newcomers read this board.
If Ancestry doesn't remove the photo, try quoting some of this (to an Ancestry supervisor if need be, not the tree owner):http://www.ancestry.com/cs/legal/rulesofconduct
"No Ancestry member or visitor to the website may:
.... B. Post, transmit, or display content which is protected by copyright or trademark or that does not belong to you and that you do not have authorization for use from the owner of the copyright or trademark, including but not limited to email messages and notes in GEDCOMs. Read our copyright policy for more information.
C. Post, transmit, upload, or display content which contains proprietary or confidential information that you do not have a right to transmit. For example, but not limited to, posting any photos of living individuals without their permission or posting anyone else's email addresses without their consent."http://www.ancestry.com/cs/legal/CommunityGuidelines
"Don't post any photos of living individuals (other than just you) or anyone else's email addresses without their consent.
Don't include identifiable information about living people without their direct consent, or, in the case of minors, the consent of their parent or guardian. This includes (but is not limited to) a person's full name, location or contact information."
> Who can remove content from family trees?
"If you have a concern about information that someone has posted about you or a living family member please contact Member Services." http://ancestry.custhelp.com/app/ask
Another member, BurgessDonnelly may have some other tips/contacts to get the photo removed.