The real question here is: can you control your taste for blood by yourself? Man’ari Eredar can control their “taste for destruction” or their evil part easier than San’layn for the blood. The same thing could be said for the Void Elves and if they can control the Void without being a part of it.
Void Elves and San’layn have the same problem: can you control your powers and your instincts without becoming an “evil character”? Void Elves must control their Void powers and the San’layn must control their blood powers. Void Elves can become “crazy” with the Void meanwhile the San’layn can slaughter people by instinct just to get more blood.