As far as I know, no college specifically teaches students how to use only one make or model of camera at the expense of all others, so why do they insist on doing exactly that when it comes to software packages?

I don't think that Adobe Photoshop should be banned, but I do feel strongly that they should not be teaching 'Photoshop', rather they should be teaching DIGITAL IMAGING, good practice, techniques and methods of working with digital images. How to crop and adjust images for print and screen use. They should teach about resolution, file sizes, file types, the possibilities and limitations of resizing, colour profiles and working with layers.
These processes can be carried out equally well using a range of software both proprietary and open source, Photoshop is just one of the options.