I've always been spoken to and treated nicely by Police Officers as an adult except the one that spiked my drink at a bar but we won't go there right now.
The last time (at a former workplace), the officer was relaxed, polite and happy, then as he turned to see the reason for the visit - a 'friendly' community one in a school - he changed instantly started bellowing 'SHUT UP - if you've got a problem with that, you'll have a problem with ME', approaching the kids as though he was squaring up for a fight.
They were a bunch of 13 and 14 year old boys of Caribbean and West African heritage and all they had done was walk up whilst chatting amongst themselves. The same kids who had held the door open for me when I walked into work that morning, helped carry boxes of paper upstairs to the photocopier and were a pleasure to run a needlework and knitting club for. And he spoke to them not just as though they were pieces of shit, as though he only needed me to turn my back for an instant and he'd be battering them.
I doubt they will ever forget that.