Here is a script using jq to remove all collections:
#!/bin/bash
#User must be logged out for the script to work
if ! command -v jq &> /dev/null
then
echo 'Please install jq'
exit
fi
set -e
session_key="$(bw login --raw)"
read -p "Organization ID: " organizationID
bw --session $session_key sync
organizations="$(bw --session $session_key list org-collections --organizationid $organizationID)"
echo "You are going to delete the following collections: "
echo $organizations | jq ".[].name"
read -p "Are you sure? (y/N) " -n 1 -r
echo
if [[ $REPLY =~ ^[Yy]$ ]]
then
echo $organizations | jq ".[].id" | \
xargs -n 1 -t bw --session $session_key delete --organizationid $organizationID org-collection
fi