Where do the speaker's allegiances lie in "A Modest Proposal"? What social groups does he identify himself with?
Literally, the speaker in A Modest Proposal identifies with the English imperialists, calling for more stringent measures to ensure British dominance over the Irish people remain unchallenged.
However, the lengths to which the speaker in A Modest Proposal goes in asserting British dominance betrays the fact that the essay is satirical and that the author, Jonathan Swift, is being ironic and is subtly advocating for the Irish and identifying with their plight.
The 1700s saw the people of Ireland in abject poverty and completely under the thumb of the British people. However, their plight was so extreme that unrest was almost a certainty, making their British occupiers take culturally aggressive measures to prevent a revolt. For example, the British anglicized many of the place names in Ireland during their long occupation and even prohibited the Irish from speaking their native tongue.
In Swift's A Modest Proposal, the speaker begins with a reasonable-sounding description of the economic plight of the Irish people, insinuating the potential for a political uprising. His solution, though, is so outlandishly overboard that it calls into question the other measures that the English had taken against the Irish in the past: buy children from their parents and sell them to the poor as meat.
Swift's allegiances are firmly with the Irish. In "A Modest Proposal" as elsewhere, Swift satirizes British control over Ireland and its baleful effects, specifically in relation to the economy. Under British rule, the common people have been turned into objects for exploitation; they are no longer fully human and have become little more than cogs in a gigantic wheel in the growing mercantile economy. Swift takes this development to its logical and absurd conclusion, putting forward the notion that babies could also be regarded as having purely utilitarian value as well as their parents.
At the same time, Swift could be very critical of the Irish. He subscribed to the dominant British stereotype which saw the Irish as being feckless, lazy, and superstitious. Swift was implacable in his opposition to measures by successive British governments that damaged the Irish economy. Yet he also expressed immense frustration at the chronic inability of the Irish people to diversify their economy, which made them more dependent on an indifferent Great Britain. Although Swift displays a certain degree of sympathy towards the Irish poor, it's important nonetheless to acknowledge the ambivalence with which Swift regarded his native land and its inhabitants.
In Swift's "A Modest Proposal," the speaker's allegiances certainly lie with the Irish poor. He is speaking with irony when he says all of the nasty things he says about the poor.
Specifically, he mimics the English view of Irish people. He imitates their bigotry and prejudice.
He certainly degrades the Irish poor if you take what he says literally. But he goes so far overboard, that once the speaker reveals what his proposal actually is--use poor Irish children for food to alleviate poverty--the reader understands that he is being ironic.
Concerning the second part of your question, the speaker doesn't really identify himself as part of any particular social group. That's not relevant. He certainly identifies himself with the Irish poor, however.