The Morality of Masturbation

Is masturbation by a mature adult who is fully choosing it in order to satisfy sexual desires, a grave sin? I'm talking about Christian adults who simply see nothing wrong with this. But under Protestantism, we have to sift among different, biblically informed pastors to figure out the answers to these pressing moral questions and they disagree amongst each other. Is that really how God intended the church to function for believers? Now a Protestant could say the following in response to this argument: So what Catholics aren't united on this issue either?"