It enters my mind that if you believe in the Devil or in demons or whatever you admit or presume that "evil" is a real thing, and have the burden of showing that this is so.

Now, lots of bad things happen to all of us.  Typhoons blow, volcanoes erupt, diseases come and we age and die.  None of that, though, is "evil."  It is just what is -- and all have both good and bad aspects to them, depending on viewpoint.

People too do bad things -- they steal and kill and whatever.  Do these things have a good aspect?   I rather think not -- some more subtle perspective is needed -- the harm the criminal does harms the victim and also harms the criminal (in either a karmic way or in the Western sense of accumulating sins).  We know, however, that the criminal is motivated mainly by the same sorts of desires and drives that motivates all of us to do bad things -- they are just less inhibited, perhaps, or less intelligent (they don't get away with it).  I find it hard to say that my impulses -- my ambition, my pride, my libido, my desire to have others like me, and so on.  These are desires derived from the subconscious -- even deeper down -- and evolved as instincts that get modified and made acceptable by our acculturation and morals and so on, and it is hard to say that an instinct evolved for natural reasons (survival of genes) is somehow "evil," even though sometimes it leads to harm.