Having your own ideas about people does not necessarily mean you have to tell them. I think it doesn't work most often. You may find an occasional one that you can be direct with. Others you have to finesse it with. That's not necessarily bad. You have to remember that they may be expecting something from you, because of their past experiences, that in fact you are not going to do to them.

And yes, I've met quite a few people who hate you because you try to do good. I guess you have to try to do it in spite of them.