In standard English it may be considered condescending and even offensive to some people.
However, as stated above, there are certain contexts and places in which it's appropriate. In the American South, it can be used as an affectionate term of address for acquaintances (e.g., as in the movie title Driving Miss Daisy).
(Just so you know, "Mr. Peter" might be used as a pet name for a man's genitalia.)