The original Karate Kid is still a classic after all these years. I can't honestly tell you how many times my friends and I did the whole "wax on/wax off" thing or even the move Daniel (Ralph Macchio) does at the end of the movie. Having said that, movies made in the 1980s were held to a different standard than that of today. First and foremost, the PG-13 rating did not exist when this movie came out and even if it had, I'm not sure that this movie would have received it based on the criteria of the day.
First the bad--Daniel wants to learn karate to get revenge and to hurt the guys who beat him up and stole his pride. The Cobra Karate Dojo makes viewers aware that "strike first, strike hard, no mercy sir!" and "fear does not exist" are rules to live by. The instructor is a hard-core ex-Vietnam vet, who clearly never left the jungles of the war (it doesn't exactly paint Vietnam vets in a positive light). The Cobras are bullies who are cruel, smoke dope, and rule the school. The language of both them and the rest of the teens in the movie save Alli (Elisabeth Shue) is terrible. I'd honestly forgotten how much bad language is in the movie. Some parents will not want their young children to experience the violence of karate as well. There's a scene in which Mr. Miagi is drunk and singing in Japanese in remembrance of his late wife, who died in Okinawa during World War 2. Parents might want to explain to their children that drunkenness does not solve problems, but rather mostly makes them worse.
The movie, however, is also full of positive images as it's a true underdog story. Some kids will be able to relate being the new kid in town from far away, having a mom that's single, and being bullied at school. The movie teaches about ultimately being accepted by others, dealing with being an only child of a single mother, fighting is not the answer, and people from different levels of the caste system can still love each other despite one being poor and one being rich. Mr. Miagi (Pat Morita) teaches Daniel that fighting is not the answer but that karate is rather used for self-defense. In the end, kids learn that hard work pays off, underdogs can win, and that bullying/hurting people is never a good thing.