I don't find these arguments convincing, because I don't think that a social obligation translates directly into an individual obligation (or, for that matter, vice versa). The argument goes like this.
A social group, of any kind, is not identical to the set of all its members at a given time. For example, Canada is not identical to all Canadians now. This is because social groups persevere over time and do not change, despite changes in membership. (That is, if social groups do change, it is not because the membership changes, but because of other factors.) Canada is still Canada (it didn't become, say, New Zealand) despite new Canadians arriving and being born, and old Canadians leaving and dying.
In a similar fashion, then, any property a social group has is not identical the sum of (or some other combination) of all the similar properties of its individual members. (The qualifier "similar" in front of properties is needed, because there are some properties social groups have that individual members lack, and vice versa. Canada has a national bird, and I do not; I have two cats, and Canada does not.) The size of Canada is not identical to the sizes of all Canadians now, nor their sum, nor their product, nor any other combination. And obligation is just another property -- I can have a particular obligation just as I can have a particular size, shape, or colour.
So far, so good. However, there must be some relation between social properties and individual properties, just as there are between social groups and the individual members. If everyone left Canada tomorrow, there would be no Canada any more; if all Canadians decided to dissolve the country and create a new one, then Canada would cease to exist. That is, although there is not an identity relation between the social and the individual, there is some sort of relation -- something like supervenience or emergence -- that holds between them. (Why am I ruling out reduction? Because in order for there to even be a problem to solve, it must be that the social cannot be disposed of in favour of the individual, and vice versa. If there is no such thing as a social group, then my problem vanishes. However, the claim that there aren't really any social groups is one I find deeply implausible.)
These relations are, however, transformative: they take something of one kind and make it into something of another kind. For example, it's sometimes argued that there is an emergence relation between the mental and the physical. That is, physical properties of the brain are transformed into mental properties. But, in this transformation process, new things are created: electrochemical reactions between neurons become thoughts and feelings. So, in the same way, if one of these transformative relations holds between the social and the individual, it follows that the properties of the social are transformed from the properties of the individual. Therefore, social obligations are transformed from individual obligations.
From this, it follows that if there is a social obligation not to support Wal-Mart, because it is destructive of smaller businesses, there is no immediately corresponding individual obligation not to support Wal-Mart. Instead, there might be an individual obligation to support smaller businesses. Similarly, if there is a social obligation to oppose gun control because it would lead to further erosion of liberty, there is no immediately corresponding individual obligation to oppose gun control. Instead, there might be an individual obligation to support gun ownership.
In other words, what we must do has only indirect impact on what I must do (and probably vice versa). And it is morally fatuous to claim that I have the same obligations as we.