The carefully worded letter appears reasonable, except what purpose was conveyed other than forcing the universities to incur high litigation fees? Using ADA as a weapon to purge free sharing of collective intelligence is despicable. I understand universities have limited resources and priorities for their enrolled students, but they should retaliate out of principles.
The community can help with providing captions. Charing $1 fee. Routing the money to a charity. Anything is better than removing the content because that is the complaint's end goal.