You can use [exiftool](http://owl.phy.queensu.ca/~phil/exiftool/) to remove the orientation tag:

    exiftool -Orientation= /target/dir/or/File

Replace `/target/dir/or/File` with the files and/or directories you want to process. If run under Unix/Mac, use single quotes to avoid `bash` interpretation.

* To suppress the creation of backup files, add `-overwrite_original`.

* To recurse into subdirectories, add `-r`.