I don't get how that supports the opposite of what salvation stated. Of course they wouldn't be silent forever after. The text clearly seemed to emphasize the importance of Peter's words by bothering to mention the fact that everyone went silent. If you notice, the Acts only tells us a simple summery of what Paul and Barnabas had to say afterwords. It gives us nothing of the same word for word emphasis of the words of Peter. There was no silence following the accounts of Paul and Barnabas.
Clearly the described narrative sequence emphasizes role of Peter at the council.
“There was no silence following the accounts of Paul and Barnabas.”
Actually, there was:
Act 15:13 And after they had held their peace, James answered, saying, Men and brethren, hearken unto me:
What follows is an emphasis on James words, including the phrase “wherefore my judgment is,” and then the conclusion.
The Catholics are pathological in reading things into the text that simply aren’t there.