There's a difference between ignorance—even willful ignorance—and active malice.

If the Peruvian government lied about why it wanted the weapons, and our government believed them, then our government is guilty of ignorance and stupidity, but not malice.

If the Peruvian government lied about why it wanted the weapons, and our government knew there was a possible issue but sold them the weapons anyway, that's willful ignorance, but still not malice. Consider the following scenario: Your neighbour borrows a kitchen knife from you, saying he needs to chop some vegetables. Instead, he uses it to kill his wife. You knew that he and his wife had a bad relationship, and you've told him off when you've seen her with suspicious bruises, but you weren't expecting anything like this. Still, you provided the weapon, and you didn't try to step between them. To what degree are you guilty? Should you have interfered in their relationship? That's where I suspect we're at: our government not agreeing with or encouraging the Peruvian government's behaviour, but not shunning the perpetrator or making any real attempt to stop what's going on. Like it or not (and I don't like it), this is really common in international relations. If the original headline had used "ignores" in place of "supports", I would agree with it 100%.

If the Peruvian government told the truth: "We want these weapons to kill and maim our own people," and our government still sold them, then that's malice and would make the headline accurate as it stands. But I doubt that's what actually happened.