To be fair, given that Stansted Airport station is a grim, cold, echoey concrete box with virtually no natural light, no facilities, and no discernible architectural merit, it’s hardly surprising that GA staff forced to spend extended periods in such an environment might become a bit surly. I find it depressing enough to pass through that (in combination with the poor rail connections, admittedly) I often prefer to go from Kings Lynn all the way down to Gatwick for my work trips to Copenhagen, rather than use the much nearer Stansted.
That said, the issues with their ticket checking are ridiculous - they insisted on checking my e-ticket when entering the station from the airport as well, and it.was extraordinarily slow. Especially pointless as XC always check tickets on the train, so those of us heading towards Cambridge, Ely or Norwich get checked twice