Not propaganda at all. I actually read everything I come accross, some of which is research notes. From what little I gathered a Necromancer may have have some noble goal at the begining but as they learn more and gain more power through what they learn they change. Sounds a lot like the Dark Side of the Force, I agree, but there's little room for doubt. Unless the mage's will is extremely strong Necromancy will corupt the user's soul.
A better parable would be money. In many, many cases, this has been true: the more you have, the more you want. I reckon it would be the same with necromancers, but with knowledge isntead of capital. To have power over life and death, however supposititious that power may be, must be extremely seducing, much more so than money, and both "enlivening" and "satisfying" at the same time, like with all kind of power.
I don't like the whole "corrupting souls" talk, by the way. Make it sound far too simple and black and white. Necromancy isn't corrupting anybody, if anything, the people using it are corrupting themselves. If they, for example, would "specialize" in Destruction, or Restoration for that matter, they would use it the same (well, in an equal) way.