He went with the messengers of Cornelius, who had come searching for him, and discovered God already at work in the household of this Roman soldier, a Gentile. What happened in Jerusalem on Pentecost occurred again, this time among Gentiles. And Peter could not help but baptize them, drawing them into the covenant. Of course, when Peter returned to Jerusalem, you better believe he faced into some strong criticism for what he had done. Perhaps some of the words spoken to him then were seeking him harm, to pull him down as a leader.
Some people just do that so naturally.
But others were, no doubt, very sincere in their objections. They wanted to do right by God. Any new beginning will encounter criticism, constructive or destructive. Sorting out which is which is not easy. All we each can do in the face of criticism, good or bad, is to do as Peter did.