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I hasten to remind you that people are people; they are neither inherently evil nor good. In most fantasy works, people can side with either good or evil. Take, for example, The Lord of the Rings... The same can be observed in Heroes, so, considering the human faction and some "fantasy principles," everything looks quite logical.

I wouldn't call Chaos purely evil magic. Good-aligned dwarves are quite capable of wielding Chaos, especially fire magic. However, Chaos in the Silvan Elves is a paradox. They shouldn't have it. Chaos and harmony are incompatible concepts, as Mdanс already pointed out. A summoning skill would look much better for them. Remember the fourth game. I repeat, Chaos is not "evil" magic; Darkness is the only magic that can be considered as such. There is a real chance to upgrade Chaos for 3 "good" and 3 "evil" races, meaning the chance of it appearing is no less than 8%. This is neutral magic (if you can call it that), just like summoning.

However, the statement "Magic is not tied to ideology in any way" is simply not true... Do I really need to explain why dwarves like Chaos and fire, why undead prefer Darkness and summoning, and why Silvan Elves like Chaos, etc.? This is precisely what is explained by their ideology.
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And I perfectly understood your situation. In exactly the same situation, you can take the extremely useful Light skill for a demon. You can even put Blindness on a forest elf's arrow and blind three stacks at once... But these are all isolated cases. Personally, I don't feel any better knowing all this, because, with a high probability, you still won't have a city with the magic you need, and even if you do, the magic might not appear.