I'd say that both sides have a point.
Firstly, the pax has a schedule change, which means that timings of the layover will be different. This may impact arrangements during that layover and could be reason for cancelation.
On the other hand the airline sold a ticket from EWR to HNL. Assuming the departure and arrival times at those two points are still the same, the airline delivers exactly what it promised. The stop at LAX was not something the customer purchased as a product, what was purchased was a roundtrip EWR-HNL. The only obligation that the airline has is to bring the pax from origin to destination within the original departure/arrival times. If the pax _had_ to be at LAX the pax should have purchased the flights with a stopover at LAX, and not just EWR-HNL.
Personally I would say that the change is reason for cancellation (and I suspect FB will allow it too), however some employees may argue the other point too and try to hold the OP to the cancellation fees.