People make mistakes... not everyone is going to get all of the rules right all of the time. I don't expect them too...

As a customer, I just hope that there is a policy and procedure in place to double-check / verify what the visa requirements are, and that it can get done before a flight leaves, if I arrive before the minimum check-in times...

There shouldn't be one person responsible for making this decision, with no recourse for a second look.