He used his taser because that is how he was trained. He isn’t trained to use discretion or judgement.
If the suspect has a weapon (any weapon) and will not respond to commands then force must be applied.
I can buy that in certain age groups, but discretion is part of being a reasoned officer, and Tazering an 80 year old woman with a cane causes me to question if this officer is incapable of using good judgment. He sure damaged my ability to think so.