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.

The issue of whether or not Swift goes too far in "A Modest Proposal," is an issue of taste.  It's a satire, of course, so the speaker has much freedom in what he writes.  He also uses irony.  Both satire and irony often use exaggeration as tools to accomplish their purposes.  So, again, the writer has a great deal of freedom to work with.

The question is, though, even within the accepted norms of satire and irony, whether or not what Swift does is in bad taste.  His proposal and his descriptions, etc., are certainly grotesque, and his central idea strikes at the core of humanity--cannibalism. 

Ultimately, however, though the essay probably is in bad taste, Swift decides that using bad taste is worth the risk.  The essay shocks the reader, and probably would not have done so if it weren't in bad taste.  The bad taste of the proposal is part of the point.

In the end, each reader probably decides whether the essay is in bad taste, whether it goes too far.  I love the wit and the humor and the satire and the irony.  But that doesn't mean another person wouldn't find the essay in bad taste.   

Swift's purpose is to shock his readers with his very "immodest" proposal. In Ireland at this time, there is extreme poverty, overpopulation, and an unfair balance of trade with Great Britain. He suggests that the Irish should sell their children as food to reduce the overpopulation and poverty. Of course, the reader is aghast at such a suggestion, and Swift's purpose is to glean this reaction from the reader. He wants us to know that people should not be dehumanized as a number but should be treated with kindness and compassion.

I don't think he goes too far because he effectively uses irony and satire to get his point across. Sometimes, this is what it takes to make people sit up and take notice of the existing problems in society.

The purpose of Swift's satirical essay is to call attention to the problems that were being experienced by the people of Ireland.  He wanted the English (who ruled Ireland) to realize what they were doing and to put in place reforms that would solve the problems they had helped to cause.  So that is the purpose of the essay and what he is trying to reform.

I do not really see how you can go to far in a satire.  I mean, he's not really suggesting that people actually do this, so how can it be going to far?  So no, I really don't think he has gone too far.