1. Slavery
The most important reason was that the Southern states were determined to preserve slavery. Slavery was a major part of the Southern economy and culture, and Southerners feared that the federal government would try to abolish it. The compromise of 1850 included the Fugitive Slave Act, which required northern states to return escaped slaves to their owners. This was a major victory for the South, and it helped to convince Southerners that the compromise was a good deal for them.
2. States' rights
Another reason why the Southern states would not accept the proposal was that they were opposed to the federal government's increasing power. The Southern states believed that the federal government should be limited in its powers, and they were concerned that the compromise would give the federal government too much power over the states.
3. The Wilmot Proviso
The Wilmot Proviso was a provision that would have banned slavery in any territories acquired from Mexico. The Southern states were strongly opposed to the Wilmot Proviso, and they threatened to secede from the Union if it was passed. The compromise of 1850 included the Compromise of 1850, which allowed for the popular sovereignty to territories acquired from Mexico. This meant that the people of each territory could decide for themselves whether or not they wanted to allow slavery. This was a major victory for the South, and it helped to convince Southerners that the compromise was a good deal for them.
In conclusion, there were several reasons why the southern states would not accept the proposal. The most important reasons were that they were determined to preserve slavery, they were opposed to the federal government's increasing power, and they were strongly opposed to the Wilmot Proviso.