Your point seems to have practical utility in the conversation about “spiritual-evil” lending a kind of proof to show evidence of absolute moral/ spiritual truth.
Even if you cut out any evidence of demonic manifestations or super-natural-evil activity, the kinds of actual, sinful horror (not just at the movies) and atrocities we’ve seen in the world make the denial of evil impossible.
In the conversation of good and evil it is much more difficult to get everyone sitting at the table to admit what constitutes something which is good: Ethic debates have a lot of leeway to discuss the context of what makes “good” good, and whether “good” exists in an absolute sense (versus a relativistic sense). But when it comes to the topic of evil the leeway-dynamic completely changes. There becomes almost zero wiggle room to deny the existence of evil. To demonstrate this, all you have to do is address things like rape and horrific abuse of children, holocaust treatment and other unspeakables, and only a fool will dare to object to the fact that there are definite absolutes that ACTUALLY DO exist when it comes to evil.
This can give the Christian a favorable entry point to throw a wrench into the spokes of moral relativism and to take steps to reasonably proceed to explain the basis for these things.