"If they are starving and getting money for their interviews, Mark may be helping these people. If they are using the money to fund their addiction, this monetary reward is only adding to their downward spiral."

I haven't watched this particular Youtube channel because I live in a big city and see the kinds of people featured on there all the time, and even talk to them. But I have to say that if the film maker is paying money for interviews, and the subjects use that money to buy drugs or alcohol, the responsibility is pretty much on the subjects. This falls under the heading of "Thinking I know what's best for someone else". If the number one item on someone's "to do" list for the day is to find enough money to score crack or buy a bottle of Night Train, and they are given that money for any reason, they're going to have a good day. YOU may think that the addict has spent the money inappropriately, but it was THEIR choice, and incidentally one of the few they get to make over the course of a day.

Get over the idea that you or anyone else can change other people's behavior or attitudes, since you can't unless you are willing to put in a whole lot of more than whatever the film maker is giving these folks. If you want to do a homeless person a solid, give them some money. They will appreciate the gift, since that's what it is. Don't worry about how they will spend it because once the gift is in their hands it is no longer your responsibility.