Today's first reading tells of what happened AFTER Peter went to the home of Cornelius the centurian and baptized the "whole household" (incidentally, this is one of those passages we refer to in support of infant baptism). Anyway, what happened after the Holy Spirit came down upon the Gentile gathering in a manifest way so that Peter just knew he was not supposed to "hinder" (another key word in baptism texts) their baptism?
This is what happened: Peter got called on it. Not that there were any "higher ups" to call him on the carpet (he was, after all, the "Rock" on which Jesus built his Church). But when there is one of you and a whole lot more of "them," "they" can call you pretty much any way they want to. There's power in numbers. "You entered the house of uncircumcised people and ate with them."
It wasn't an observation. It was an accusation.
Peter did not get all defensive, though. He explained the situation, starting with his roof-top prayer in Joppa. Everything could be attributed to grace, and none of it to Peter's personal initiative.
And "they" surrendered to the same grace. "They stopped objecting and glorifed God."
That's how it's supposed to work in the Church even now.