For example: this classic.
You may see a person dedicated to charity works but whilst at the same time either abusing the children (in words, deeds) or others outside in the workplace he is exploiting his workers by overworking them, giving low pay (Unfair wages which would be different if you were their own son/family member or race/religion with the same qualifications) etc.
Thus, “judging” by the “appearance” looking at that “charitable act alone” doesn’t prove much.
One Day, God Will Reveal all (outward deeds to our intents in our hearts). May God have Mercy.