A man came to visit a Rav that was not well to do the mitzvah of bikur cholim. WHen he got to the Rav’s house he saw the rav sitting by the table learning. He was all better. The man sighed and said, “What a shame that you are better, I wanted to do the mitzvah of bikur cholim.”
When we do a mitzvah, we need to remember that it is for the other person, not ourselves. You should be THRILLED that there is enough NEW clothing for these suffering people, and they do not need to further lose their dignity by wearing used stuff. I can’t imagine where a slap in the face comes in.