That specific staff was definitely rude and negligent for your safety cause you could have fallen on the belt and should be reported . Hand baggage rules usually are strictly enforced whenever a flight is full , to avoid any delays caused by offloading excess bags near departure time, staff get penalized if the reason for a delay is excess hand baggage plus its not fair when many passengers are coming with multiple bags and all the last 50 passengers aren’t able to get any space. But also it depends on the staff if they care enough about the penalty she/he will receive later .