Fans did not respond well to changes with their favorite shows. Many questions were being asked like where is the blood? What happened to the intense dialog? Where is my fan service? The main reason for censorship comes from the fact that anime appeals to many young kids because it has many cartoon elements. The broadcasting companies that tend to air these shows such as Nicktoons or Cartoon Network aren't allowed to show some of the mature content found in anime. Unfortunately this terns off a lot of people who might potentially enjoy the show because they think of it as little kid shows. However, Cartoon Network airs uncut anime on Saturdays from 11:30pm-6:00am so that many of the adult fans can enjoy their favorite shows the way they were supposed to be.
Any censorship that you see in anime and mange comes from Japanese censorship laws one example being, Article 175. Which states that any person who distributes, sells or publicly displays an obscene writing, picture or other materials shall be punished with penal servitude for not more than two years or be fined not more than two million and a half yen or minor fine. The same shall apply to any person who possesses the same with the intention of selling it. The big question is "what defines 'obscene’”, which the law doesn't answer. So that makes this law very vague and doesn't have a huge impact on the industry, but when fans see censorship a lot of it derives from this law.
Another theory for anime censorship comes from people claiming that it is a marketing strategy. With advancements in technology it has become very easy for fans to stream or illegally download their favorite shows online for free. This has led do a decrease in DVD and Blu-Ray sales. It has also lead to many dubbing companies going out of business, especially in America. Funimation is one of the only large dubbing companies left in America. Many fans believe that the censorship is an attempt to promote people to buy the DVD or Blu-Ray version because they can have their favorite shows unedited and uncut.
There are many different reasons as to why anime is censored but mainly it is treated like any other form of entertainment. Overall censorship is going to continue to happen because it is a way for the industry to respond to negative reactions people have when they see anime on TV. It is no different from someone seeing anything inappropriate on TV and complaining about it and having it censored. To avoid dealing with these nuisances I recommend purchasing or finding uncut versions of anime.