Read a bit about Diogenes if you think this is a recent question. But I do wonder, what do you think members of society should be required to contribute to that society?
shitting literally anywhere but the dead center of the street or sidewalk shows a non-zero amount of caring about how one conducts oneself as part of a society. when one stoops to the level of shitting in the middle of where everyone walks (I visited SF in 2016, and from what I understand, it has not gotten any better since), one implicitly displays a complete and utter disregard for his fellow man. shitting in any bush or patch of grass is a step up from that. even pooping in a bag (I was going to say "free grocery bag" but I suppose they don't have those in SF anymore, do they?) and leaving it in a gutter is better than depositing your feces right in the middle of a public thoroughfare!
if I woke up tomorrow on the streets of SF, homeless, without a penny to my name, and in dire immediate need of taking a dump, I would do it literally anywhere that could even be slightly considered "out of the way of other people," and it would never even cross my mind to even consider dropping a fat steamy deuce right where everyone can step in it.
when you take a shit in the middle of a crosswalk or sidewalk, you're implicitly displaying your total rejection of even the most baseline expected behavior of the society you physically reside within. this is completely obvious to anyone who has never immersed themselves in one of these decaying societies to the point where they become numb to it.