From my viewpoint, I went to college in order to prepare me for my future. If my future likely includes the use of a proprietary product, then I think it is in the best interest of both the students and the school to teach that proprietary product.
I wouldn't go to a design school that didn't teach photoshop. These days I don't think many programmers will leave college and not use git or github at least once in their career, so I don't see a school using it as such a travesty.
I guess the important part is that it should not be a requirement. Offering optional courses on products, maybe, but don't give any credits towards a degree.
After all, why do you expect to be taught photoshop? Because it's a de-facto monopoly! What is one of the reasons for it being a de-facto monopoly? Because it's being taught (as a requirement) in schools! That's positive feedback supporting that de-facto monopoly, and that's bad, as it presents a barrier to entry of new market participants. And it's highly questionable that it is good for the students that they get to depend on a de-facto monopoly for their work, as that, for example, probably makes it more expensive for them to work in the field.
For github, it's similar. Teaching git is perfectly fine, obviously, as that is free software, so the knowledge that you gain there you can use without any restrictions, teaching github is not, as that makes it easier for github to gain customers, at the expense of its competitors, and makes it more expensive for the student to become a customer at a competitor.
I wouldn't go to a design school that didn't teach photoshop. These days I don't think many programmers will leave college and not use git or github at least once in their career, so I don't see a school using it as such a travesty.