Bob, I have to call baloney on saying no capos on guitars. Many reasons, but primarily the one that might resonate best with you is that saying guitarists should not use capos is like saying you have to play a song with odd sounding voicing and inversions on a keyboard because you are only allowed to play in a certain range of notes on the keyboard. Capos allow the right chord voicing to be played to get the arrangement of notes to ring correctly.

The number of songs played with capos and alternate tunings they sound just the way they do is too long to list.

I will name one very well known example: Jumpin Jack Flash as played by Keith Richards. It just doesn’t sound right unless the guitar is tuned to an open tuning AND capoed.