Yes, beyond the moral, there absolutely were political and economic incentives to abolishing slavery, though a lot of it tied back to the moral. I do have to take issue with the characterization, though, that the Northerners in any way were motivated to "disrupt the Southern agrarian economy"--paying people a pittance and granting them the right to vote did not require the disruption of the agrarian economy in any meaningful way. Most abolitionists understood that a peaceful transition from slavery to freedom did not mean it would happen overnight. Gradual emancipation was the position of the great majority of abolitionists, as had happened in New York and New Jersey, where slavery was phased out over many decades, and which did not disrupt the economic situation of any slaveowners there. This gave slaveowners a generation or more to invest their income in other ways or else to start paying the freed slaves a low wage to keep them working on the farm (or as a house servant, or whatever the case may be). The disruption of the Southern economy would consequently be very limited, if it, in fact, would have disrupted the economy at all. Only a handful of abolitionists advocated for immediate emancipation, though there were some, like Elizabeth Coltman Heyrick.

Anyway, back to the question...

One of the big political issues that Northerners had with slavery was that it continually disrupted Northern laws and economics. Particularly, the Fugitive Slave Act of 1850 authorized the federal government to go in to Northern states and capture escaped slaves, and return them to the South. This happened without giving the accused slaves due process under the law. In the North, black people were considered full citizens, and were entitled to their day in court, so the North wanted to make Southerners prove that the accused escaped slave was, in actual fact, the escaped slave they said they were and not some other slave or, worse, an actual free person. But the South objected, and the Supreme Court famously determined in the Dred Scott v. Sanford decision of 1857 that slaves, and even accused slaves, and anybody at all of African decent, were not citizens and thereby had no standing in court or right to due process.

False accusations were a real problem. Under the original Fugitive Slave Act of 1793, Southerners would pay bounty hunters to go North to find an escaped slave, and if they couldn't find the slave they were looking for, they'd just kidnap any black person they could and tell the authorities that that was the "slave" they were looking for if they happened to run into law enforcement on their way back South. Often, they would deceive a free black person into traveling with them South under some pretense, and then kidnap them once they were somewhere that the kidnappers were less likely to get questioned or caught. The most famous case is that of Solomon Northup, a black man who was born free, who had been free his whole life, but was kidnapped and sold into slavery. He made his income working on construction projects, and as a raftsman, and sometimes supplemented his income by playing the fiddle at hotels and ballrooms. He was offered a job to play the fiddle in the traveling circus which he accepted. He traveled with the circus hiring managers from his home in Saratoga, New York, to Washington D.C. (where slavery was legal) to supposedly join up with the circus. But the hiring managers didn't work with a circus at all. Instead, they drugged him once in Washington D.C., and sold him to a slave trader as a "fugitive slave". Northup then spent twelve years on different plantations before he was able to regain his freedom, and then wrote a book about the experience--Twelve Years A Slave.

This was hardly unique. Lawyer Jesse Torrey testified before U.S. Congress about the problem all the way back in 1816, and wrote in a letter that in Delaware alone, "To enumerate all the horrid and aggravating instances of men-stealing, which are known to have occurred in the state of Delaware, within the recollection of many of the citizens of that state, would require a heavy volume."

Kidnapping of free black Northerners was big business, in fact. There was a whole "Reverse Underground Railroad" where free Northerners were kidnapped and taken South illegally. Among the most prominent Southerners/Southern sympathizers engaged in the activity were John A. Murrell, John Hart Crenshaw, and the Cannon-Johnson Gang. Kidnappers often preyed on children. One kidnapper operating out of Philadelphia spent months coaxing dozens of black children--one or two at a time--onto a boat by bribing them with fruit and sweets, and then sailing away down South to sell them into slavery. This led the mayor of Philadelphia to hire someone to go South to recover illegally kidnapped Philadelphians--and when he got there, the Southern slaveowners were uncooperative. Of the children who were recovered, many died from malnourishment and/or from beatings given on the eve of being freed from the slave owners.

The only unique thing about Solomon Northup's case was that he was actually able to regain his freedom and then wrote a book about the experience. Once sold into slavery, the kidnappers would usually destroy the freeman's freedom papers if they had them. If the freedom papers somehow survived or were recovered, judges would side with a slaver willing to testify that the freedom papers were forged. And since black people were not allowed to testify in court, there was often nobody who could make a legal case on behalf of the kidnapped person.

This disrupted the economics not only of the free person's employer, but the economics of the kidnapped person's family as well. In Northup's case, he had a wife and children who had lost their primary breadwinner, and they were worse off for it. Families who wanted a husband, wife, child, or other relative back who had been sold into slavery illegally would have to hire someone to go recover them, if they even could, which would also usually require a lawyer and a lawsuit to do it the "legal" way--another strike against the family's economic well-being, one that most free Northern black families simply did not have the resources to afford.

More generally, the people-stealing business also deprived the North of a workforce who were often willing to work at lower wages than white Northerners were willing to work for, and under more unpleasant circumstances. Because free Northern black people often faced discrimination in the North in regards to employment, they would often take lower wage jobs, often in poor and dangerous working conditions, as long as the job offered a steady paycheck. But being under constant threat of being kidnapped and sold down South into slavery, Northern businesses that relied on the labor of black Americans had an economic gripe to make.

The Fugitive Slave Act of 1850 tried to address the kidnapping issue by sending in a force of federal U.S. Marshals to Northern states, but this led to other problems, because the Marshals weren't much better or more concerned with capturing the "right" slave than the bounty hunters had been. As a result, abolitionists would try to stop these arrests of their black neighbors who were legally free under the Northern state's laws. One of the most famous cases is the "Jerry Rescue" case, a case involving an escaped slave named William "Jerry" Henry who was working as a cooper in Syracuse, New York. A U.S. Marshal arrested Jerry, only for Jerry to be rescued from the local jail by a force led by abolitionist and church minister Samuel Riggonwold Ward--he himself a former slave. Ultimately, both Jerry and Ward had to escape to Canada to avoid prosecution, yet another example of the social and economic upheaval to a community outside the South when deprived of Jerry's labor and Ward's Congregationalist church's loss of their minister.

Out West, in the non-state territories, the prospect of legal slavery was even more direct. The Missouri Compromise and subsequent Kansas-Nebraska Act, both of which essentially guaranteed that some of the territories would become slave states, threatened the economics of working class white Americans. Should slavery become legal, it would drive down the price of white labor who would be forced to compete with free black labor. Hence, slavery was deeply unpopular in the territories. But Southerners were undeterred and flooded in to Kansas on the eve of the public vote to ensure it became a slave state, by voting in favor of slavery and threatening violence against those who would stand in their way. This led to the "Bleeding Kansas" proxy war that preceded the Civil War--all due to the political and economic issues caused by slavery that the vast majority of homesteaders and laborers living in those territories wanted to avoid.

(...cont'd...)