There's a meme that Obama has been much harsher on whistleblowers than predecessors, but it falls apart on closer inspection:

https://news.ycombinator.com/item?id=5701813

The most important takeaway is that the sample size on leak prosecutions is very, very low, so happenstance alone can make a President look unusually hostile. Here, it's a combination of happenstance, a shift in media norms, and cases begun under the previous President.