Sunbathing on the sidewalk

Is apparently offensive, illegal, and grounds for calling the police. Hmmm...
I was on my lunch break, and as I've been doing for about a week now in preparation for BM's brutal sun, I was lying on the ground, head propped up on my backpack and shirt, getting about 30 min of sun.
"Sir..."
"Sir!" she said.
I rolled over, looked around confusedly for a second, and then saw the security guard on the opposite side of a fence.
"I'm going to have to ask you to not lay there. People have complained, and this is private property."
To reiterate, it was the sidewalk on a small side street off Harrison around 19th. In other words, deserted.
"What? This is the sidewalk. Its not private property," I scoffed, still confused.
"You don't have to comply, I understand you wanting to be here, but I'll have to call the cops," she softened a little-
"I don't mind you being here," she continued,
"Lots of people have complained, is all."
What people? Oh, the people up in their offices? Who complained, I wondered.
Anyway, I had to be back at work in ten minutes. I got under my skin, however. I did end up ranting to my co-workers.
Sometimes San Francisco can be way too nit-picky about shit.
If someone was laying on a quiet side street down south, I'm sure people would not only not care, but hardly even notice, much less complain.
They'd intuit that the person was "enjoying some rays," but up here, its serious business, apparently.