Air carrier pilot reported ramp agent approached the aircraft and opened the cargo door while the engines were running.

Narrative

Blocking into [Gate] XX; engines were still running and red rotating beacon was still on. I was setting the parking brake when the Master Caution went off that the cargo doors had been opened. The parking brake hadn't been set and verified; engines were running and the beacon on; and a ramper actually approached and opened a cargo door. This scares me to death as a Captain. The last thing I want is someone being injured or killed on the ramp around my aircraft. This was the last flight of the night and I actually put on a vest and prepared to go to the ramp to speak with the crew chief about why this happened and how dangerous this is. The crew chief was walking up the stairs to the jet bridge. When I confronted her about this and told her how dangerous this is; she had over ear beats headphones on! I've written countless reports about rampers with Beats headphones on and AirPods on the ramp. This is so incredibly dangerous. I told her you're the crew chief and you're wearing those headphones? You know better than that... you need to set the example. There is a shocking lack of safety culture on the ramps; and this was ZZZ terminal X. Of all places; this ramp should have appropriate management oversight. Ramp agents are pressured to open the cargo door to start their clock on the turn; and because it stops pilot and flight attendant pay when the doors are opened. This is an INCREDIBLY DANGEROUS incentive that completely endangers our crew members. Management needs to stop this practice IMMEDIATELY. How many ramp agents need to be hurt and killed before action will be taken? Appropriate oversight on the ramp needs to occur immediately. Ramp agents need to be supervised; counseled and disciplined for wearing music headphones on the ramp. This is symptomatic of a broken culture. Please take immediate correction company wide.