Many nonprofit volunteers will go out of their way to assist folks that do not even wish to be helped, and even if they are willing to take what is offered because it is free they resent the people helping them because the volunteer knows their reality and true circumstances, the facade they have created, the mask between what they project to the world and how things actually are. It is unwisely to help someone against theirs, but it is not necessarily bad to do it, if you, the volunteer is getting something out of it.
Perhaps, it makes you feel good to do the right thing or try to assist someone that you know needs help, even if they are unwilling to receive it or believe they do not need it. If you are in such a situation and you see that you are not appreciated but you continue on anyway, then you must understand why you are doing it. For instance, you might be doing it because you realize it needs to be done, or that that makes you feel responsible for doing the right thing.
Over the years, I've put in 10's of thousands of hours of my time and god knows how much money helping the common good. I've learned when it is appropriate to help and where to put my money, as well as where not to. Trust me when I tell you that you can not kindly help someone against theirs or assist someone who is unwilling to receive. If you choose to go ahead anyway, that's fine, just realize what you are doing and why you are doing it.