It is true that the narrator of Jonathan Swift's "A Modest Proposal" does not mention morals; however, just because he never mentions the word does not mean he avoids the subject. In fact, it seems to me that his sense of moral justice is what prompts his "modest proposal."
Consider the reasons he gives for wanting to enact a change. Too many women who have too many children are reduced to begging in the streets and doorways for their survival. The children, as they get older, are forced to become thieves because there is no honest work for them, to become paid soldiers for a foreign army, or to sell themselves off as indentured servants. The cause of these deplorable problems is a lack of interest by the government, and this is, indeed, a moral issue.
The narrator certainly discusses a moral issue in paragraph five when he talks about a great immorality which the women of his country are perpetrating on the innocent:
those voluntary abortions, and that horrid practice of women murdering their bastard children, alas! too frequent among us, sacrificing the poor innocent babes...more to avoid the expense, than the shame, which would move tears and pity in the most savage and inhuman breast.
Clearly he is commenting in this satirical, fictional proposal on the very real immorality of women killing their children--born and unborn--mostly because they cannot afford to feed them. While he is condemning the women for this practice, he is also noting the cause of their immoral acts--not enough opportunity for people to earn their own living.
Look next at the advantages he gives to his modest proposal. Many of them discuss an immorality, at least as he sees it, perpetrated by his country and his countrymen. Here are the conditions which are immoral:
1. Too many Protestants have left the country, refusing to pay their taxes, virtually ceding (giving up) their country to a foregin enemy.
2. The poor tenants own nothing; everything, land and cattle, has been seized by the government.
3. The rich people have all the money and the poor people are left to fend for themselves.
4. The relationships between the poor men and women are deplorable because they are starving, frustrated, and angry. The country does not encourage marriage
which all wise Nations have either encouraged by rewards, or enforced by laws and penalties.
5. When marriage is not encouraged, mothers are less caring for their children and men are free to abuse the women who are bearing their children, even kicking and beating them when they are pregnant.
All of these are moral problems which the country is facing, and the narrator ends his proposal with a call for something betters, saying his idea may not be the best; however, any new proposal should consider two things. First, will it provide food and clothes for the thousands of women and children who are without them, and second, will it provide opportunity for the beggars to be able to have something more. He adds that perhaps, under the current conditions, many people might prefer to be sold and eaten than to suffer the misfortunes he has outlined.
Everything the narrator cites as being problems in the country could be considered moral problems. Of course he is not really recommending that children should be fricasseed or sold; he is, however, suggesting that something should be done to rectify these conditions because it is the right (moral) thing to do.