It's not just the faxing that causes people to act the way Karen (supposedly) acted - it's the anger and maliciousness being directed at them by numerous people, all day, every day, even when they do try to be sympathetic to the fact that the system fucks everyone. But there's only so much empathy one can muster.
(Not to mention the various other factors that push good people out of government, such as working for decades to make the systems better only for them to get worse.)
To be clear, I agree with you to an extent; if instead of being malicious and directing anger at the people doing their best to help, people like the author more calmly expressed their frustration with the system, maybe they can bring it up with their superiors, as you said.
All of it's a mess, and not a single facet of this issue is without blame - not the recipients, not the bureaucrats, not the politicians, and certainly not the voters.
[1] A discount that was less than the delta between consumer-class and business-class prices, when the latter doesn't seem to actually be providing better availability lately.
Have you seen how much public sector employees taking calls get paid to be abused all day?
If you want people with limitless wells of compassion, pay better. Public sector jobs generally get to scrape the bottom of the barrel and compete with the local grocery store.