Plus all the trust issues of having lived in the street. Only someone who hasn't interacted a lot with the homeless would say they are just like everyone else. Even if the reason they became homeless was just random by the time they've been homeless for a couple of years they are a different person.
There's a reason many of the homeless avoid shelters, if you talked to one you'd know why, and it's not because the other guests are lovely kind people to be around.
These are regulars at that library who never caused enough disruption to be banned, and aren't dangerous enough to be in jail. They also have more to lose by getting banned than housed patrons.
That's the whole point of that post.