I totally get that frontline workers of all stripes are exposed, vulnerable and under stress, but I don't think it is acceptable to be downright rude, especially if in a situation where people are following instructions and acknowledging the situation.
Yesterday a doctors receptionist on the phone with my very stoic and undemanding terminally ill mother reduced her to tears because the internal communication at the surgery had broken down and when my Mum was explaining that she was sending samples to the surgery via myself as instructed by the doctors for the second time because they weren't labelled and sent correctly at the end of last week, and was concerned she may have internal bleeding so wanted advice from a GP about stopping blood thinners, the receptionist just kept giving her the Spanish Inquisition and saying that doctors couldn't be disturbed from their important work for something like that. It too my Mum getting really upset for a telephone appointment to be set up - she is on a special list for this as is housebound and has only used it when she is really concerned - eg suspected cellulitis advised by the community nurse requiring antibiotics.
When I went up to the surgery with the samples, the same receptionist was equally rude and obstructive to my face (masked, obviously, as I am shielding), and when as instructed I asked to pick up paper prescriptions we had been told were ready for us for controlled drugs that cannot be sent electronically, before I could get my sentence out she barked at me I would have to go home and ring in about that. I am ashamed to say I raised my voice and was very firm - the situation was resolved correctly and while my Mum hasn't made a complaint, she has spoken to the Practice manager who has agreed this was out of order - she explained the low staffing levels they are working under but still said it was no excuse and will be having a general chat - if this sort of approach can be taken and allow stressed staff to air their fears and needs to help them work through this, it may be beneficial to them as well, rather than formal complaints.
In our case, worst situation is my Mum delaying calling in for palliative support when she needs it, and things that could be managed easily at home become a problem that require more serious and precious resources. She really was left feeling as if she's been written off because she doesn't have CV19. That sucks.
As for the postie, hopefully he'll feel a bit better soon, and I am sorry that this damn virus is causing so much angst for everyone x It is so sad - best wishes to the OP and the lady she is supporting xxx