I think actually we are both on the same wavelength here, just coming from different angles. In my view it would be quite wrong to tell a teenager that masturbation wasnt ok. It's when the guilt of it causes problems that it stops being ok. I have a feeling that sex is like food in this respect. It is the guilt that causes the problems not the sexuality itself. Don't we have to go back to our roots at this point and focus upon the bigger picture? The more we focus upon the sexuality the more out-of-focus our vision becomes. The more we focus in on ourselves the more we stray from the context, which is everything.
The essential fact is that God accepts us As We Are and takes it from there. We just have only to be Wholely Honest: no wriggling, no beating-about-the-bush, no beating ourselves up either but actually isn't it the being honest which takes the courage? The desire to stand justified so that we can be free of God is the constant temptation.