Please re-read my post and note that, at the beginning of the sentence you quoted, I specifically targeted the instruction of music. More specifically, you cannot help teach a blind violinist how to prevent themselves from continuously playing their notes flat without being able to see how they are playing.
Blind people are perfectly capable of learning to play music. Blind people and non-blind people alike can learn on their own, or seek out instruction. It is the latter that we are discussing here.
Totally, and I'm sure there have been many, but being able to touch and feel the placement of the musician's hands/fingers/etc. would be important. There are certainly things they could teach without that touch, just like non-blind people could teach a few things remotely sans video, but core areas of playing wouldn't get the right attention.
I suppose blind people will never be successful with music.