There seems to be a false dichotomy here - free-for-all or no automated traders. Automated firms are included in the diagram, so Barclays wasn't hiding them. It was, however, claiming to remove those it considered bad actors, and then wasn't actually doing so. Surely allowing HFT firms but removing those (specifically, Tradebot) that didn't follow the rules would still have left enough trade flow to enable the buy-side to get value? If it's bad enough to warrant removal from the diagram, it's bad enough to be removed from the pool, leaving every other participant to continue as before.