A very naive, cliche and opinionated phrase, that is overused in modern society. This phrase is only an opinion because 1) everyone has a different idea of beauty and not everyone is going to be considered attractive by everyone and 2) there are horrible people that commit a variety of crimes everyday. It's usually used when trying to "fix" society's views in some way. People who usually say this USUALLY have the least amount of horrible experience in their life, are very confident in themselves, super optimistic or just don't have anything better to say.
Normal Girl: "I'm so ugly!"
Pretty Girl: "Everyone is beautiful (in their own way)!"
Person 1: "There are so many bad things going on in the world..."
Person 2: "Maybe, but everyone is beautiful (in their own way) no matter what!"