A close parallel to the topic of whether or not villains do evil/bad/unsanitary/unhealthy practices because they’re evil is whether evil/bad/unsanitary/unhealthy and here I’ll add /edgy practices are performed because there is a villain.
What I mean is easily encapsulated by the old trope of villain women wearing less. (see both “Skimpy villains” and “Evil is Sexy”). Back in the day, censors were a lot stricter about dress, and you could get an “uncomfortably” revealing outfit past the censor if the bad guy (I mean girl) wore it because, of course, they’re a bad guy, so they’re going to do something “bad” like wear less clothes.
Beyond the fact that this, of course, goes right to that problematic “because I’m evil!” nonsense (a female villain is about as likely to dress in skimpy clothing just because she’s evil as any person is to not wash their hands just because they’re evil) there’s two other problems.
The first is where you get into weird moral statements. With the censorship thing, you have the statement, “dressing in a revealing way is immoral and only bad people do it.” This is a belief some people, perhaps in part, hold. I myself adhere to a religion with a dress code. But at the same time, I’d never want to deliver this message – you aren’t a bad person if you dress in a way more revealing than my moral code dictates one ought to. And what if it was swearing? Yes, yes, we all know swears are bad words. So only bad people say them!
But I mean, swears are things you say in a state of frustration, and literally everyone uses them. Maybe you say “crap” instead of something stronger but that’s still swearing. Pretending like good people don’t swear and bad people do is as foolish as pretending like good people never smoke and bad people do. Look, villains are often people who murder people, are you really going to put swearing and cleavage and cigarettes up there with actual criminal acts? It’s ridiculous and doesn’t make for strong writing. That’s not actually how the world works and when writing doesn’t reflect reality, even try to, its chances of becoming campy, cheesy, or otherwise poor rise exponentially.
And I get it, I get the moral messages you’re worrying about sending – but there are actual consequences to some behavior, and actual conflicts with others, when these things aren’t just “evil” and rather than trying to equate “oh no boobs” with “oh no villainess!” or “look kids only bad guys smoke!” you could, you know, actually try to add some depth into your story by adding those consequences and conflicts in. Maybe the good guy does smoke. Maybe he doesn’t get cancer, but is short of breath or finds that he hates being dependent or that he spends so much money on the problem. Maybe there isn’t a bad consequence, not visibly, as there often isn’t in real life, because your audience should know that things are complicated.
The second is the line of thinking, “They’re allowed to do it. They’re a villain.” This is not quiiite the same as, “Because I’m evil,” but a problem for all the same reasons – and a few more. Just becasue a villain is “allowed” to do it doesn’t mean they will, yes.
Additionally, just because whatever “it” is is deemed unacceptable doesn’t mean a villain is actually “allowed” to do it – for one thing, this wording suggests it’s “okay” if you’re “bad” when a lot of the behavior is not okay ever. The villain is not allowed to murder people, that’s why they are a villain. They aren’t allowed to. They choose to do it anyway. If you get this mindset of allowed to, you’re going to get weird, stilted characters and the messages of morality are going to be weird and offkilter. Heroes don’t always do what they are allowed to do, either. Honestly, unless it’s relevant to the setting by laws and culture therein, don’t think about allowed to so much as choose to.
You can argue that we’ve made progress on not being so ashamed of the existence of bodies and so the dress thing is less relevant, but “evil is sexy” is still alive and well and arguments about “what she was wearing” are too, so…in one form or another, this weird line in the sand of “good” and “evil” based on things that actually have little to no moral value also exists. Some things are wise or unwise, healthy/sanitary or not, desireable to one and not another, and people are all mixed bags, so to try to put everything into neat little columns of “good” and “evil” and then carefully tuck those items into your respective “hero” and “villain” boxes isn’t going to get you rich characters. You don’t have to draw a line every single time. There certainly are some lines that have to be drawn, and those are the lines you should be fighting over – because that’s the point of heroes and villains.