Define "practical reason".
Protection of a individual's rights.
No, because killing someone is to deny someone their most fundamental right; the right to live.
No, because you're forcing someone to do something they don't want to do, which is against their rights.
Infringes upon a person's right to own property.
Infringes upon freedom.
People have a right not to be harmed by others.
Protection from harm.
If a person wishes to die so that their organs can be used to help others, that's their choice. Forcing someone to die against their will in order to harvest their organs is murder.
Harassment, any kind of harassment, is a form of harm to a person's well-being.
Corruption is usually a form of theft.
Making something illegal because it hurts another individual is a moral issue, not a practical one, I'm afraid.
It's moral, but also practical.
Do onto others as you would have them do onto you is a practical rule, society functions at its best when everyone observes it. If people stop observing it, society begins to fall apart. Hell, even animals will generally stick to that rule when it comes to their own kind, are you saying that they view it as a moral issue too?
I presume that your stance is that prostitution is not hurting anyone, and that none of the prostitutes could be considered victims unless they were literally, physically forced into prostitution. And this is where you and I appear to have an ideological difference: I don't really believe that.
Prostitution does cause harm to most women, that's why I want it to stop. Women that have been forced into prostitution, either by threats of violence, or they are being forced to by economic circumstances, should be helped out of prostitution. However, if a woman feels that the risk to their well-being is worth the reward, that's their choice, and I choose to respect that.
Well, I guess the Irish are just the better people then. Or less into smoking.
We sure are an exceptional people.
But banning alcohol would be far too difficult, and the last time it was attempted in USA didn't work out too well.
Banning heroin hasn't worked out well either, it's still on sale, and it's lining the pockets of unscrupulous criminals.
This doesn't mean that I don't think that people who are in favor of banning tobacco or alcohol do not have a very good case. However, the use of cigarettes and alcohol is too widespread, popular and socially accepted for an outright ban to be effective. Slower, more gradual and subtler approaches seem like a better idea.
The thing is, heroin use is widespread, popular, and part of the culture of a part of our society, banning it hasn't changed that. Alcohol, despite the dangers, is accepted because it's a part of the culture of the majority. While I don't necessarily agree with the claim, I have seen some say that it's a form of discrimination by the majority upon the minority, and I can understand why those people feel that way.
But there is a difference between leaving something legal that's already legal, and legalizing something that is illegal (and very severely prosecuted). Every such change is a big experiment and you have to wonder what effects it would have. Legalization is also an act that sends a message that a certain thing is basically "OK" and acceptable from now on. Now, what exactly is the reason to do this with heroin?
The thing is, I don't have a moral objection to heroin use. I think that it's stupid, ill-advised, dangerous, and that there are better ways to escape from life for a while, and I would tell anyone that tried to use heroin exactly that. But if they choose to do it anyway, if they just don't care about the consequences, I don't feel that I have the right to stop them. Judge them, certainly, but not stop them.
You got me there, I have no evidence, just a common sense observation of human behavior that tells me that people are far more likely to buy something if it's available on the market, cheap and easy to get, than if they have to go out of their way to get it.
I've said this twice already: Legalisation should mean that it's harder to obtain, not easier.
If you want to buy heroin right now, it's simple: you go to a dealer, tell him how much you want, give him money, someone else hands you your stuff. It takes 20 seconds. If you were to buy it legally you'd have to go to a store, get IDed, pay for it, you get it in a package that contains all sorts of warnings and, ideally, you pay more for it than you would by getting it from the street.
Sure, people who really want to buy heroin will find a way to do it. But I'm more worried about many other people who would not go out of their way to get it, but will not be against trying it if it's right there and if they don't have to worry about getting harassed by the police for it. I wouldn't be surprised if, the moment is became legalized, a bunch of people jumped at the opportunity to finally try it out of curiosity, which they were previously too afraid to do.
I am a cynical person that considers the majority of people to be stupid, but even I don't think people are that dumb. People would try pot, ecstasy, all the various forms of soft recreational drugs, but when it comes to heroin and harder drugs, I think people would be wise enough to stay away. Especially if buying it meant it coming with warning labels plastered all over the product.
Making it illegal for people to buy sexual services? Treating prostitution as form of violence against women (or men, if the prostitute is male)? Nonsense! And can you believe it that, at the same time, abortion is legal in those countries! Not to mention that most of them have TVs in their homes. 
Particularly funny are comments by user called Jes: "A country that is full of men who sleep with men , women who "marry "other women should not be forbidding a man who prefers paying for sex" and "Personally , I think that prositution is good for a country that has so many people living alone with no change to have real sex. I also think that it will save a lot of cold marrieges from collapsing . Its better for a man with a tiny penis to buy sex and return to his artless cold wife thereafter than having an affair with a workmate who is eqaully bored at home" 
)
So you're saying that most people now believe that the reason it's illegal is because the governments are selfish and just won't let them enjoy the good stuff?
We have some planes, and they can theoretically shoot bullets, but they're not fast nor powerful enough to take down a passenger jet. Our main strategy is to create an international image of us as lovable drunkards so that nobody has any reason to invade.
