It’s the ‘the customer is always right’ philosophy, clearly by someone who has never worked retail or services.

It's not a defence, it's just reality. Abuse is real. Using IP addresses to combat abuse is very broken – I too had carrier-grade NAT when I lived in a developing country in the past – but it does work. Abuse prevention is hard, but very much required. Abuse prevention with zero false positives is nearly impossible with the current state of technology. So yes, "it happens" because all of this is hard. You can pretend the problem doesn't exist, but that's denying reality.