That's a tough one.
I do think something needs to be done on a drastic scale to address some of the issues such as drug usage, veterans on the street, and untreated mental illness. But I don't know about taking away their rights if A. They are not harming anyone or themselves B. they are not receiving endless benefits (i.e. free phone, medicaid, food stamps, etc) from the government without work/volunteer/disability requirements and C. if they are not a burden on society or causing any kind of disruption such as keeping a trashy camp, begging, etc. Some people are just roamers and are happier that way even though I'll never understand it.
What can we do as Christians to help those who don't want our help? IMO, not a lot. I think of the verse
Matthew 10:14 where it speaks of not being welcomed, to shake the dust off your feet. Not everyone will listen to the message you have. Some people are content in their sin or their chosen way of life even if it is undesirable.
The broader question of how we can help those who don't want help can be stretched out to other people who are living miserable lives and could get whatever help they need but don't want to change. I personally was extremely close to someone who has a family yet has not had to contribute to society and has always lived off of everyone else's generosity and kindness. This person was offered mental health, counseling, medical help, church help from a wonderful church, dozens of jobs in which they would blossom and finally be able to support their chronically poor family and they were gifted hundreds of thousands of dollars of things to help enhance life and reduce stress in an effort that alleviating some main stressors would encourage them and give them a hand up.
But in spite of all of that, this person chose to be abusive, entitled, ungrateful and not to receive any of the hands up - only the handouts and if the handouts went away or were reduced, this person would turn against the ones giving it, claiming they were not Christian and didn't want to help a poor person like the Bible says to do. Eventually I and others have had to step away from this person because they will not get the help they need. They are depressed, miserable, and have a negative outlook on life - but blame everyone else for it and they are content in their misery.
So I have this mentality of "let them" if they are so desperate to be miserable/homeless/destitute. I believe the single most powerful thing we as Christians can do for these sad souls is pray for them.