This question was brought up in Sunday School, under the heading of, "Is it sin to..." and I found myself getting really irritated. If one considers it a sin to give, or to not give, let them live according to conscience, or, as some claim they are able to 'discern the Spirit', according to the moment by moment directives of the Spirit, but to use the excuses I hear them use, as to why they should not give, to me is reprehensible. If they KNOW the guy is going to use the money for drugs, that is one thing, but to assume he will is another. "Do unto others according to what you would have them do unto you" makes a lot of sense and is usually an easy decision.
The principle behind, 'You shall open wide your hand to your brother, to the needy and to the poor, in your land.' and, 'But if anyone has the world’s goods and sees his brother in need, yet closes his heart against him, how does God’s love abide in him?' (if you see a brother in need, and have it with you, shame on you if you do not give it to him). I can tell you this: It is easier to give someone else your last $20 and be done, (if you have enough left to get home on), than it is to take the person and give them a job, or take the time and effort to get to know them and learn their habits and faults to deal with them according to THEIR conscience.
But this is just another of many examples of people finding excuses to do as they wish. I find it specially telling when they look until they can find a Bible verse or precept to support their selfishness. (But yeah, I too will be measured by my own standard.)
On a lighter note: 'Give a man a fish, and you will have satisfied his hunger for an hour; but teach a man to fish, and you will have satisfied his hunger for life!' --==-- 'Give a man a drink, and you will have slaked his thirst for an hour; but teach a man to drink......!'