Remember when Xykon killed a bunch of self-righteous Paladins...

[hroþila]

The 3.5 Monster Manual: "The process of becoming a lich is unspeakably evil and can be undertaken only by a willing character."
The alignment entry for the lich template says "Any Evil".
Liches are pretty much all evil by the rules.

Personally I take that just as a requisite to qualify for the template in the first place, not as a subsequent restriction (the way druids, paladins or bards have alignment restrictions). The Libris Mortis might say that a non-Evil lich is a conceptual oxymoron, but it still says they can exist, which is all that matters here, since nobody is saying they're common or likely, just that they're possible.