The "Acts of the Apostles" is a record of the earliest days of the Church. Days of formation and, in a special way, days of forgiveness.
Try to imagine how Jesus' original followers felt when, after that first Easter and Pentecost, scores of people who had either persecuted or ignored him, joined the ranks of the disciples and became converts and teachers of the Gospel. Human nature being what it is, we can be sure that their welcome into the hitherto exclusive little club was not always a warm one.
The third chapter records how Peter was concerned with healing old wounds and with fostering unity. Notice, however that, in the process, he does not whitewash the past. In fact, he comes on very strongly as pointing right at them, he cries out: "You disowned him. You put to death the author of life!" Can't you just see the old guard disciples urging him on? But Peter's intention is not to humiliate. "Turn to God for forgiveness, for I know my brothers and sisters that you acted out of ignorance."
I can't help but conclude that these charitable words were directly inspired by that great prayer of forgiveness which must have meant so much to this guilt ridden fisherman. "Father, forgive them for they know not what they do!"
The ignorance to which Jesus and Peter refer is an ignorance that tends to distort our perception of one another. It seems to be part of our imperfect nature that we rarely, if ever, see people as they truly are. Some are given this extraordinary gift by God. I am thinking of insightful and saintly confessors of the past such as the Cure of Ars and Padre Pio.
As for the rest of us, our image is filtered. We are never completely objective. We look at each other through lenses clouded and distorted by racial, social, and religious prejudice, by past experiences, by "things" we have heard, by cultural perceptions, by relative position within family, organization or profession. We look and interpret through lenses clouded by our own fear and insecurity, by psychosexual immaturity etc. etc.
Through this haze we judge each other. classify each other, love and hate each other, hear and ignore each other, help and hinder each other, praise and condemn each other.
In all cases, in so far as the objective reality is blurred by these subjective elements, there exists real ignorance. Ignorance, which, because it is a condition in which we all share, cries out for understanding and forgiveness. We all know how it hurts to be rashly judged, to be classified and maligned. We have all suffered in these ways; BUT what we frequently forget is that we have all caused others to suffer in the same way.
Many of his contemporaries misjudged Jesus due to preconceived notions of the Messiah, due to prejudice against hill country people from Nazareth and a host of other reasons. Later on, many of them, because of the example of the Disciples, saw the light...saw the real Jesus. One reason why the Apostle's example was so effective was their closeness to Jesus and their consequent understanding and accepting attitude, their spirit of reconciliation and their humble recognition of the ignorance which blinds and limits us all and the distorted view of each other which so often results.
As Peter said, "Turn to God and to each other for forgiveness, for I know, my brothers and sisters, that you act out of ignorance."