Explain how the fugitive slave act violated the core principles of american democracy

The origins of these acts go back to the constitution where the article 4 has a clause called the fugitive slave clause which orders states to deliver up fugitives from labor (euphemism for runaway slaves) when they are requested by slaveholders.

This clause was translated into the first 1793 statute which was basically a civil statute that was not well enforced according to the southern states, thus leading to the creation of the 1850 fugitive slave act.

The 1850 act was tougher than the previous one, punishing not only runaway slaves, but also people who harbored or aided slaves in any way, with civil and criminal penalties including up to 6 months imprisonment if caught and prosecuted successfully.

There were many documented cases of people being tortured and imprisoned in south because of helping fugitives.

These acts directly violated the democracy in several ways for example:

One clear example would be the movie "Twelve years a slave" which depicts the documented case of Solomon Northup, a free black man who was sold as a slave without proof of him being one.  

usually her father was the one that controlled it after the death of the husband