“You think like a litigious American. The guard thinks like a British soldier. There is a difference.”
Yep, while they wear “fancy” dress uniforms, they are real soldiers with a job to do. Their duties and SOP’s are well established, and in their culture in their country, it is understood that yelling and physical altercation (minimal with escalation as needed) is proper when guarding royals and royal estates. They are security. They are not playing games. Don’t like it? Then follow the rules, and don’t mess with the guard.