Interfering to others life sounds really awkward. A person who has no work in his own life and have enough space in life only have extra time to interfere on other's life.
Not sure about others but I consider it such a bad manner. According to religious views it consider as such a sin. Interfering may have so many type, such as interfering someone's personal life or someone's professional life without any permission.
If we individually say someone not to interfering in my life it may sounds rude but we at least can try to request. If after requesting he continuously doing the same interference what to do I really don't know the language we should use to make them stop.
Most of the time these kind of people interfere in our personal life and try to learn about the weak point of us and try to harm us or gossip behind us. They don't even have common sense of having permission before interfering to other's life. Whatever, we can't change them, so what to do next?
At first I'll try my best to avoid these kind of people around me and keep distancing may help me, if they trying to follow me and investigating on my personal life I only can pray to God for rescuing me from such kind of people around me.
Not only in personal life but also in professional life we can found such kind of people and they don't know the manner when they trying to interrupt. Some don't have self respect and they repeat the same mistake after requesting them not to interfere in our life. They are just helpless to correct themselves and we can't help them too.
We all need a life with no problem but why some people are always ready to create problems, don't they think if they plan trap for others they also can fall into the trap they are creating? This is really very funny when I saw them fall into the trap they plan for others. I believe in live and let others live, don't interfere on other's life. My life is not your story to tell others right?