Water is not a commodity, it is a human right. Without it we die. To restrict access to or deny water to anyone because they are poor or to cause them illness or death because of that denial in lieu of personal profit is a human rights abuse.
"but it might be an effective population control tactic"
You're thinking too much like a government with that comment. I have no doubt governments have deliberately sat by watching this all happen to take advantage of it as well. Look at the Arctic, melting rapaciously and yet governments sit and wait until it melts enough for them and their corporate proteges' to drill it and suck it dry to make more profits instead of working now to mitigate and adapt to the effects already being felt. It is truly a false choice, as if they think that climate change and water scarcity will not affect their lives... that is why they don't care. They will all have theirs when it all breaks loose.
To commoditize water is to leave millions of poor people on the edge of poverty, thirst, and even death. And just as with the "food crisis", when you have thirsty people they will take anything if pushed to the limit, even if it means they use all of their money (what little they may have) for water to have nothing left. Those who do not believe that need to actually look at what is happening in the developing world. Private companies do not have to think about "quality".... Just making the most profit from the dirtiest water. It is immoral to the core.
Addressing the issue of water sanitation combined with scarcity and waste due to agricultural methods and climate change is the first step in bringing people in the developing world out of poverty. However, organizations like the World Bank, IMF, and WTO really don't wish to do that. A level and equitable field is the last thing they want.
So where do we draw the line in allowing these organizations to be able to dictate to people whether or not they will have access to the water they must have and have a right to in order to sustain themselves?
If you own the water, you also own the food. And if you own the food and water, you own the people. This is the grand scheme of it all, and in collusion with private companies and governments these organizations are setting the stage for a future where water and food are controlled by a handful of multinational corporations that will dictate your life.
It is not sustainable, it is not ethical, and it is not humane. People must stand up for their water rights and to see water remain a public trust.