Why did many in Missouri object to letting Kansas become a free territory?

The Kansas-Nebraska Act was an 1854 bill that allowed settlers of the terms of the Missouri Compromise of 1820 would become a free state. The question of whether the territories would be slave or free would be in 1861 after an internal civil war, southern states had begun to secede from the Union.

it may be touching on the issue of over sexualizing all women