Probably, as far as many of his contemporaries were concerned, this proposal did go too far, especially if they did not understand the text's ironic and embittered tone. Swift's point is that the situation between the wealthy English and impoverished Irish has already gone too far. He suggests that, if the English are content to treat their Irish brothers and sisters with such a lack of humanity, if they are willing to figuratively "devour" Ireland's land, resources, and government—which has resulted in terrible poverty among the Irish—then it does not require much of a leap to suggest that the English literally devour the Irish too.
In the end, the narrator even references other possibilities that could be used to alleviate the suffering of the Irish, saying,
. . . let no man talk to me of other expedients: Of taxing our absentees at five shillings a pound: Of using [no products] except what is of our own growth and manufacture: Of utterly rejecting the materials and instruments that promote foreign luxury: Of curing the expensiveness of pride, vanity, idleness, and gaming in our women: Of introducing a vein of parsimony, prudence and temperance: Of learning to love our country . . . Of quitting our animosities and factions . . . Of being a little cautious not to sell our country and consciences for nothing: Of teaching landlords to have at least one degree of mercy towards their tenants. Lastly, of putting a spirit of honesty, industry, and skill into our shop-keepers, who, if a resolution could now be taken to buy only our native goods, would immediately unite to cheat and exact upon us in the price, the measure, and the goodness, nor could ever yet be brought to make one fair proposal of just dealing, though often and earnestly invited to it.
However, he says, that he doesn't want to hear about any of these possibilities until "there will ever be some hearty and sincere attempt to put them into practice." In other words, there are other ways of increasing English wealth, methods that require industry or frugality (and are thus less appealing). As the English have chosen not to adopt any of these, Swift does not go too far by ironically suggesting a less-palatable (pun intended!) alternative.