Take a look at this: http://aviation-safety.net/news/newsitem.php?id=2134
Interesting doctoral thesis that indicates that criminal actions against pilots or air traffic controllers can be damaging to flight safety as a whole. According to the article, deterence effect of prosecution is minimal and prosecution might even have detrimental effects on flight safety! My take is that it is not possible to remove prosecution totally, but the approach to prosecution should be better thought through to prevent negative effects highlighted in the article.