The seceding states talked about it plenty if you look.
South Carolina
The Southern States now stand exactly in the same position toward the Northern States that our ancestors in the colonies did toward Great Britain. The Northern States, having the majority in Congress, claim the same power of omnipotence in legislation as the British Parliament. "The general welfare" is the only limit to the legislation of either; and the majority in Congress, as in the British Parliament, are the sole judges of the expediency of the legislation this "general welfare" requires. Thus the Government of the United States has become a consolidated Government, and the people of the Southern States are compelled to meet the very despotism their fathers threw off in the Revolution of 1776.
The consolidation of the Government of Great Britain over the colonies was attempted to be carried out by the taxes. The British Parliament undertook to tax the colonies to promote British interests. Our fathers resisted this pretension. They claimed the right of self-taxation through their Colonial Legislatures. They were not represented in the British Parliament, and therefore could not rightfully be taxed by its Legislature. The British Government, however, offered them a representation in the British Parliament; but it was not sufficient to enable them to protect themselves from the majority, and they refused it. Between taxation without any representation, and taxation without a representation adequate to protection, there was no difference. By neither would the colonies tax themselves. Hence they refused to pay the taxes paid by the British Parliament.
The Southern States now stand in the same relation toward the Northern States, in the vital matter of taxation, that our ancestors stood toward the people of Great Britain. They are in a minority in Congress. Their representation in Congress is useless to protect them against unjust taxation, and they are taxed by the people of the North for their benefit exactly as the people of Great Britain taxed our ancestors in the British Parliament for their benefit. For the last forty years the taxes laid by the Congress of the United States have been laid with a view of subserving the interests of the North. The people of the South have been taxed by duties on imports not for revenue, but for an object inconsistent with revenue – to promote, by prohibitions, Northern interests in the productions of their mines and manufactures. … The people of the Southern States are not only taxed for the benefit of the Northern States, but after the taxes are collected three-fourths of them are expended at the North. This cause, with others connected with the operation of the General Government, has provincialized the cities of the South. Their growth is paralyzed, while they are the mere suburbs of Northern cities. The bases of the foreign commerce of the United States are the agricultural productions of the South; yet Southern cities do not carry it on. Our foreign trade is almost annihilated.
Florida
The majority section may legislate imperiously and ruinously to the interests of the minority section not only without injury but to great benefit and advantage of their own section. In proof of this we need only refer to the fishing bounties, the monopoly of the coast navigation which is possessed almost exclusively by the Northern States and in one word the bounties to every employment of northern labor and capital such a government must in the nature of things and the universal principles of human nature and human conduct very soon lead as it has done to a grinding and degrading despotism.
Robert Toombs of Washington, Geo., who subsequently drafted the Georgia Secession Declaration put it this way in a speech before the Georgia Legislature in November 1860: “At the last session of Congress they brought in and passed through the House the most atrocious tariff bill that ever was enacted [i.e. the Morrill Tariff], raising the present duties from twenty to two hundred and fifty per cent above the existing rates of duty. That bill now lies on the table of the Senate. It was a master stroke of abolition policy; it united cupidity to fanaticism, and thereby made a combination which has swept the country. There were thousands of protectionists in PA, NJ, NY, and in New England, who were not abolitionists. There were thousands of abolitionists who were free traders. The mongers brought them together upon a mutual surrender of their principles. The free trade abolitionists became protectionists; the non-abolition protectionists became abolitionists. The result of this coalition was the infamous Morrill bill - the robber and the incendiary struck hands, and united in joint raid against the South.â€Â
Georgia
The material prosperity of the North was greatly dependent on the Federal Government; that of the South not at all. In the first years of the Republic the navigating, commercial, and manufacturing interests of the North began to seek profit and aggrandizement at the expense of the agricultural interests. Even the owners of fishing smacks sought and obtained bounties for pursuing their own business (which yet continue), and $500,000 is now paid them annually out of the Treasury. The navigating interests begged for protection against foreign shipbuilders and against competition in the coasting trade. Congress granted both requests, and by prohibitory acts gave an absolute monopoly of this business to each of their interests, which they enjoy without diminution to this day. Not content with these great and unjust advantages, they have sought to throw the legitimate burden of their business as much as possible upon the public; they have succeeded in throwing the cost of light-houses, buoys, and the maintenance of their seamen upon the Treasury, and the Government now pays above $2,000,000 annually for the support of these objects. Theses interests, in connection with the commercial and manufacturing classes, have also succeeded, by means of subventions to mail steamers and the reduction in postage, in relieving their business from the payment of about $7,000,000 annually, throwing it upon the public Treasury under the name of postal deficiency. The manufacturing interests entered into the same struggle early, and has clamored steadily for Government bounties and special favors. This interest was confined mainly to the Eastern and Middle non-slave-holding States. Wielding these great States it held great power and influence, and its demands were in full proportion to its power. The manufacturers and miners wisely based their demands upon special facts and reasons rather than upon general principles, and thereby mollified much of the opposition of the opposing interest. They pleaded in their favor the infancy of their business in this country, the scarcity of labor and capital, the hostile legislation of other countries toward them, the great necessity of their fabrics in the time of war, and the necessity of high duties to pay the debt incurred in our war for independence. These reasons prevailed, and they received for many years enormous bounties by the general acquiescence of the whole country.
Texas
They have impoverished the slave-holding States by unequal and partial legislation, thereby enriching themselves by draining our substance.