CS I understand entirely your frustrations. I've seen people like the OP wandering the streets of LA, or downtown Boston, or any other of the places many of the uncared-for mentally ill end up here in the USA (now that there's no such thing as mental health care for the uninsured).
They wear tin foil hats, or signs proclaiming some nonsense 'great truth', but it's just their mind that is damaged in some way. I've spoken to a few of these people over the years, and I must say my primary responses have always been pity and sadness that such people cannot find help (even if they were interested - the ones I've met have no idea, generally speaking, that something is wrong with themselves, and spend hour after hour trying to explain their thoughts to anyone who will listen - as if it's us that just aren't getting it).
Family members and old friends have long ago given up on them - in many cases understandably so, as they can effect no cure. Frequently modern medical science can do nothing except drug them into submission (if they tend to the violent).
I'm confident that at some point in the future we will have effective treatments for such brain mis-firings (assuming the human race doesn't implode - or explode - or kill the planet, a distinct possibility).
I remain sad that people like the OP have to go through their only life in this manner - I can personally do nothing. Sometimes I am slightly relieved if they have access to what they need in terms of secure housing, clean water, healthful food - and a few friends to talk to. That appears to be a tiny minority, however - at least here in the USA. The majority disappear into the edges, wandering the back alleys and hallways, sleeping in parks (or dumps), prey to criminals and the religiously insane.
Human civilization is a thin layer of 'approved' behaviors, easily stripped away - at heart, we appear to be no more than self-aware apes, fighting each other for a bigger piece of the banana. Those who cannot keep up, for any number of reasons, are left in the dust - ignored and cast out. Add in a life lived in Fear, Isolation, or Economic Insecurity (all of which describe the current state of the USA) and there's no hope for people like the OP.
Sadness and Pity is all that is left.