It's only natural. Very little can be done about it. Only those with sources get the best information, and it's hard to develop a source without having some empathy with the person who is that source. In this particular case, the entire defense and intelligence establishment seems to regard Snowden the same way. When you hear something enough times, it's hard not to adopt it as your own belief (assuming you weren't inclined to believe that in the first case). It's just the way we're wired.
Consider this fascinating experiment, which is not one to one with what I'm talking about but certain a cousin to it: