It will eliminate solo village spellcasters who have any real power. I'm thinking these spellcasters aren't the sorts of people the average joe is going to willingly seek out because his neighbor's dog pissed on his camellia bush every day running for the last month. It will also, I think, focus the evil into a few well-protected locales, and entrench it, and cause it to recruit and train new talent, and to develop a bureaucratic hierarchy. The laws of magic 1. Spells in latency tend to remain in latency unless acted on by an opposite force.
Aligned spells attract.
Unaligned spells repel. Negative magic begets negative reactions. Positive magic begets positive reactions. Every spell used to compel the behavior of any living creature against its will carries a negative alignment. Every spell used to inflict harm, damage, pain, or death, no matter the nature of the target, carries a negative charge.