This frightened naturally enough those who were already Christian. They knew that he had been a persecutor was this a genuine change, was he trying to insinuate himself into Christian circles to better know who were following Christ. Worldly wisdom says that leopards do not change their spots. Older people can often be very cynical about the possibilities of change and sometimes we might even say to one another about another person that he or she will never change. That is not really a Christian option.
People can and do rise to the challenge.
The truth dawns on them. I think realistic and true, but also a bit bleak. Our Lord was saying there are no regular Father Christmas goodies, no gentle escapism for the followers of Christ. This Gospel is saying that even if we are doing the right thing, even if we are united in prayer and faith to Christ the Son of the one true God and actually producing pretty decent fruit regularly in our family and in our work, in our circle of friends, that even then the branch will sometimes be pruned to give more fruit. I suppose any of us who have lived for a while know, or perhaps from our own personal history or the history of those around us, that sometimes the pruning can be very heavy.