I cannot understand why people behave so badly. If all sorts of things mess up your day so you turn up late, perhaps some blame should lie with people responsible for that, but there's no way the GA is responsible for that. Even someone with pretty well zero IQ would understand that. So why shout at the GA? It's not her fault, she's merely following procedures.
Sadly, I know the answer to my own rhetorical question: usually it works and, if it doesn't, nothing is lost. I remember having lunch with a friend of a friend who proudly told me that, when priority boarding was announced for people with disabilities, she marched straight up and claimed she had disabilities (she has none). If questioned, she merely shouts the GA down. I now regard her as untrustworthy, and I'm afraid it also calls into question my friend's judgment in remaining friendly with her. But the point is that this lady leads her life in that way. She's a bully and a cheat and knows that she will never have to face the consequences.
Sadly, after recent events with Dr Dao etc., it's giving every imbecile a free license to behave abonimably.