Those who say “How can he be a Christian, he uses dirty words” are unaware of the difference between crude uncultured speech and cursing.
Cultural refinement might follow faith but it doesn’t constitute faith.
Consider how different the Greek of 1st Peter and 2 Peter looks. Peter picked up a new style. Peter was a believer in both books.
A more morally experienced Donald isn’t necessarily going to look like the locker room joking Donald of ten years prior bragging on what a sex object he is seen as (even though it was true).