And why are people this way? Why do people feel the need to consume mood altering substances?
There is not a single answer to that question. However, genetics and personal circumstance play a large role. More people turn to mood altering substances and more often, when they under persistent stress and living in impoverished conditions. That goes for all addictions, including gambling, sex, and substance abuse. You shoulder your opinion upon the path of least resistance to you and simply say, all of these people cause their own fate, and deserve whatever consequences that come, but surely you also realise that is a very oversimplified view. You could have said the same for women, coloureds, and native/indigenous peoples back in the day (and perhaps still currently), because the statistics would show that their behaviour was not normal, and hence not acceptable. It is a mistake to think that we need to change these peoples' behaviour in order to solve the problem. That will only work where there is reasonable facility and capacity for the person to do so, and part of the reason why we have frowned upon groups of people in the past is because statistics show that providing a facility for that change does not necessarily lead to a change in capacity or the resultant behaviour. The black man was at a time treated as vermin, and whenever the black man behaved accordingly or reacted in a way to challenge it, it was seen as unacceptable behaviour. More recently the black man has been accused of being aggressive and violent, but even the statistics don't agree with that. People still may associate the black man with violence, because they are more likely to be frustrated by the disdain that some members show to them, and display behaviour that may appear to represent aggression. Its no different with any minority of people. The biggest determinant, shown throughout history, of behavioural outcomes, do you know what it is? Social expectation! We all have a a sense of what is 'normal' or 'expected'. It is our nature to notice when things differ from what we expect, it is how we learn, and in my personal opinion also makes life somewhat interesting. To turn around however, and say that our behaviour toward minorities has no bearing on their behaviour, is saying therefore, that you consider them to be non-human. The result is that society builds a culture of condemning all differences, and by our nature, continually frustrates us. To blame the victim is simply consistent with that ignorant view. If they are not a victim, providing them with the chance to prove it will do no harm to your own personal judgement. Prohibition is an antiquated philosophy, it is simply necessary at an extreme point, and even then there is always much more (in the vast majority of cases) to a person than what they have done. We are talking about a herb that is labelled a drug and an addictive substance because we find its use undesirable. If we ignore that the behaviour of users is influenced by society, we will not improve upon the problems we perceive as actually happening, because their behaviour alone is enough for you to believe it. Their behaviour, aside from anything else, is also a result of what society deems 'normal'. To shift your view beyond black and white gives room to allow what is normal to have a rethink, and will make you realise that nothing is black and white, they are simply standards we either accept or reject, and we accept or reject them based upon our experience. If you are not willing to challenge your experiences, you simply cannot change, and you simply cannot see the better outcome.
It may turn out that societies view of what is and is not normal is a larger causal factor than anything else. We associate what is normal because that social facility is advantageous for us in family and peer groups. We need to see the advantage of understanding groups of people beyond our experience and comfort, because whether we like it or not, we all affect each other, so we all need to establish a means of residing in peace when no violence is sought.
To seek a world that is no different from what your experience tells you it is, is to seek ignorance, it is to seek conflict with other groups whose only crime is that you feel threatened by them. Violence does not exist without conflict. At that point the only thing left is the hope that they will just go away, but soon enough someone will throw the first rock, and you will rationalise that you were right about them. Yet, you will have no perception that they too will think themselves right about you, but they have far more to fear as a minority than you. They may even think that you only understand violence. Its a dangerous place to be, but accepting only your experience as truth will inevitably bring you into conflict with others who offer a different opinion, and having a difference of opinion makes no difference to you unless you feel threatened by them being the majority, and you have no way of knowing what they want if your door is closed to them. Acquiring acceptance, freedom, respect, and understanding are hardly things you need to worry about.
And going the other way by saying that all people are created the same, is a rather convenient interpretation of being created equal, for the majority.