> That's the reason you've lost empathy for them, because they are humans who have to shit and are denied access to toilets?

Oxytocin--the hormone critically involved in empathy and social behaviors--has been linked to toxin-elicited and socially-mediated disgust [1]. If that link holds, it suggests why public defecation is the emerging turning point of the debate.

Rhetorically, this means trivializing the problem is unlikely to be successful. People will lose empathy for people who shit on their street. On the flip side, this offers a well-scoped beachhead. Solving the public defecation problem could rebuild empathy for San Francisco's homeless and give political oxygen to the broader, more-intractable problem of homelessness overall.

(I'm honestly shocked nobody has run for office in San Francisco on a vision zero-esque pledge to eliminate public defecation.)

[1] https://onlinelibrary.wiley.com/doi/pdfdirect/10.1111/gbb.12...