If your photos are still managed in Aperture, the simplest solution is to remove the unwanted keywords there rather than deleting all metadata.

Two methods mentioned:

• Select the affected folder/project, then select all photos and use Metadata > Remove Keyword (or remove all keywords if that’s acceptable).
• Better yet, open Window > Show Keywords HUD, select the unwanted keyword such as “iPhoto Original”, and delete it. You can do the same for Face-related keywords.

This removes those keywords without wiping the rest of your EXIF/IPTC data.

If you need to work on files outside Aperture, command-line metadata tools like ExifTool or jhead can also edit metadata, but the community answers don’t give a specific workflow for them. For the easiest and safest approach based on the answers provided, use Aperture’s keyword tools to delete only the unwanted tags.