The Southern Democrats did not like the compromise of 1850 because they did not want California to be introduced as a free state.
Step-by-step explanation:
The compromise of 1850 was declared to settle the tension over slavery between North and South America. North did not favor slavery whereas southern America favored slavery.
After the Mexican-American War, the question of expansion of slavery into the acquired territory gave rise to tensions. When California applied for statehood or a free state, Southern Democrats thought that they would lose tie between free and slave states and so did not support the compromise.