This passage of 1 Peter is one of the clearest statements that Peter makes that he is writing to people who are not Jewish, but Gentile and pagan. You can see his statement in 1 Peter 4:3-4.
Peter uses a very general word here that can be translated either or “pagans” or “Gentiles,” from which we get the word “ethnic.” It is a general word, and most of the time, it is translated as “Gentiles,” but the usage of “pagan” here is appropriate, because it speaks more to the immoral behavior of the culture than an ethnic description. Peter is writing to people who were once a part of that behavior, and have since repented and walked away from it. However, they still live in such a society, and the draw of temptation and the world’s pull is a strong one. So Peter writes to encourage them.
Those who have watched his readers leave that lifestyle simply don’t understand it. It makes no sense to them, and they think it strange that someone would deliberately not join in with them in such reckless living. It disturbs them to the point that they “heap abuse” on believers, which is the Greek word for “blaspheme.” This indicates that not only do they defame and slander believers, but they do the same to the God of those believers as well.