To aid and abet evil is defined as providing any good or service that is beneficial to the evildoer with full knowledge that the evildoer has or will commit a moral crime.
If you sell weapons to a mass murderer or someone who you know will commit mass murder, his crime becomes your crime.
If you provide food, water, clothing, or shelter to a mass murderer or someone who you know will commit mass murder, his crime becomes your crime.
If you lie (and lying implies you know it's a lie) about the mass murderer's crimes in order to help him evade justice, his crime becomes your crime.
If you provide misinformation about the mass murderer's crimes due to a genuine lack of knowledge on your part (or because you yourself received misinformation), you are innocent.
If you sell food, water, clothing, shelter or firearms to a mass murderer, and you do not know that he is a mass murderer or that he will commit mass murder, you are innocent.
Given the clear, simple, and common-sense rules above, it is clear that politicians either don't get it or they deliberately break this moral rule. Those who break a moral rule due to a genuine lack of understanding of morality may be forgiven if they show repentance and make an effort to pay restitution. Those who deliberately break moral rules are evil, for the definition of evil is to deliberately defy morality.
Politicians who knowingly sell weapons to mass murderers and torturers are guilty of committing a moral crime and should face criminal charges for this.
If you knowingly sell weapons to mass murderers and torturers, and these crimes are committed, then you have intentionally enabled mass murder and torture to occur. You are now guilty of mass murder and torture. What you do unto others, others may do unto you.
Do not allow evildoers to evade justice. Unopposed evil will only lead to the proliferation of evil.