In the chapter "Rich and Poor," Singer's consequentialist dismissal of the distinction between killing and allowing to die lends rhetorical power to his argument for wealth distribution (a consequentialist view of responsibility, which refuses to see a moral difference between acts and omissions, serves better to illustrate the crimes of capitalism than a non-consequentialist view of the same does) . In Singer's view, "we cannot avoid concluding that by not giving more than we do, people in rich countries are allowing those in poor countries to suffer from absolute poverty, with consequent malnutrition, ill health, and death" (_Practical Ethics_ 222). As you note, unfortunately Singer puts it in terms of an individual obligation to help, in other words, charity: each citizen of any affluent nation has a moral obligation to give as much as he can, without thereby sacrificing anything of comparable moral significance.
There are a couple of things Singer may have taken from his study of Marx. Singer's criticism of Locke and Nozick faintly echoes Marx's:
***** If we build up our theory of rights by imagining, as Locke and Nozick do, individuals living independently from each other in a 'state of nature', it may seem natural to adopt a conception of rights in which as long as each leaves the other alone, no rights are violated....[I]f I do not make you any worse off than you would have been if I had had nothing at all to do with you, how can I have violated your rights? But why start from such an unhistorical, abstract and ultimately inexplicable idea as an independent individual? Our ancestors were -- like other primates -- social beings long before they were human beings, and could not have developed the abilities and capacities of human beings if they had not been social beings first. (227) *****
Also, in the chapter "Ends and Means," Singer offers a consequentialist criticism of unthinking oppositions to the use of violence: "If the objections made to the acts and ommissions distinction in Chapter 7 were sound, those who do not use violence to prevent greater violence have to take responsibility for the violence they could have prevented" (308). Here, Singer uses Engels's _The Condition of the Working Class in England_ effectively to illustrate his point: "Whether or not 'murder' is the right term, whether or not we are prepared to describe as 'violent' the deaths of malnourished workers in unhealthy and unsafe factories, Engels's fundamental point stands. These deaths are a wrong of the same order of magnitude as the deaths of hundreds of people in a terrorist bombing would be. It would be one-sided to say that violent revolution is always absolutely wrong, without taking account of the evils that the revolutionaries are trying to stop. If violent means had been the only way of changing the conditions Engels describes, those who opposed the use of violent means would have been responsible for the continuation of those conditions" (309). In this sense, utilitarians may be friendlier to socialists than Kantians are, though I agree with you that utilitarianism fundamentally suffers from its lack of safeguard against an organicist justification that lives of the few may be unceremoniously sacrificed to increase the total happiness of society at any time.
Yoshie