Why "Purity" Is An Overrated Character Trait

Unfamiliarity with "bad" things: This would ultimately be harmful to the "pure" person, as xe would have no experience with negative and unpleasant things to help xir cope when (not if) something bad when it does happen. Also, a person who is pure in this sense is likely to make some very bad decisions, as xe'll lack the experience and knowledge to recognize the red flags leading up to to something potentially wrong or disastrous or know enough to read the fine print, literally or figuratively. Also, being unexposed to bad behavior doesn't prevent a person from behaving badly - young children tend to figure out how to lie and hit all on their own.

Inability to cope with "bad" things: A liability for most of the same reasons as above - being unable to emotionally handle bad things in life leaves a person in dire straits indeed. In fact, this is what usually happens in stories with these characters. But rather than having the character make an effort at learning to cope, it usually ends up with the character having a big strong protective love interest to cuddle and kiss the emotional trauma away (until it happens again). In reality, people who need and use people thus are emotional vampires and anyone who had to put that much effort into maintaining someone else's emotional state would sooner or later end up a drained emotional mess xirself.

Lack of "negative" emotions: "Negative" emotions aren't necessarily bad. Wanting to have nice things (the basis of greed) isn't a problem until one treats others unfairly to get them. Feeling a visceral reaction against something you don't like (hate and anger) is Nature's way of telling you you're dealing with a threat, and this isn't a problem until one does things like refusing to consider that the hate/anger may be unfounded and irrational, or that one's reactions to the subject of hate/anger are unfair and overblown. On the other hand, hate and anger can motivate someone to try to do something that is a genuine problem - if you feel angry about the fact that someone got wronged, you're more likely to try and set it right than otherwise. It's not the absence/presence of "negative" emotions that make one's character, but rather how one deals with them.

Some characters actually have the ability to wipe out or erase negative emotions from people, which is often used to neutralize or even redeem enemies. But when you think about it, this would realistically likely only be a temporary fix - it does nothing to teach the affected person how to deal with future negative emotions in a healthy way. Neither does it necessarily address the root of the problem - if the person behaved destructively out of anger built up from being treated inconsiderately, you'd likely just see the same scenario play out again eventually if people continued to treat that person the same as before.

Having "pure" intentions: Just because one has good intentions in what one does doesn't mean that the outcome will be desirable or that the methods are just. One could act on the "pure" desire to make a loved one safe and happy, but end up making that person feel smothered and stifled instead. One could have a "pure" desire to govern a country justly and fairly, but still lack the skills/knowledge necessary to create a system of laws and governance that actually works, resulting in the country being no better off than when a tyrant was in charge. One could have a "pure" intention to keep a country/city safe and end up chasing/punishing scapegoats and people who were never a real threat in the first place, or creating laws/programs that don't really work or create worse problems in the long run.

Moral purity: A recipe for disaster for multiple reasons. First, different people have different ideas of what constitutes "moral" behavior, and so many (if not most) people will find your character coming up morally short in a few areas. Secondly, many people will find the whole thing pretentious and presumptuous, particularly if you character's "moral" behavior involves chastising or lecturing people on relatively trivial matters (EG, slight rudeness), or for things they think aren't really that character's business (EG, how a casual acquaintance should be parenting a teenager), or for being preemptively snarky or violent to a "bad" character who hasn't even done anything bad yet (which basically makes the "moral" character a bully).

Sexual purity: AKA virginity. This is a neutral trait; it has no bearing on how kind, caring, responsible, and competent a character is, which are traits that matter.

Purity of beauty: Again, this has no bearing on whether a character is a good person or not, so vaunting a character up over the "purity" of xir good looks comes off as shallow and pretentious. Plus, physical beauty is largely subjective.

Of course, these traits on their own don't make a character bad or even a bad person necessarily - perfectly good characters and good people can be beautiful, chaste, adhere to moral codes, etc. But they don't really make your character an especially good or worthy person, either.