What sorts of events made civil liberties so important for the founders?
To me this is a very broad question. I'm more looking for events of things that happened that made civil liberties so important. More like why were they even came up with in the first place.
The Founders were concerned with civil liberties because of various actions by the British government that seemed to create a state in which the government could do whatever it liked in the way of searches and seizures and trials.
For example, in the early 1760s, a case was brought in Massachusetts challenging the legality of things called writs of assistance. These were essentially open-ended search warrants. They allowed the government official holding the writ to search wherever he wanted, whenever he wanted. This allowed the government to search anyone's home without having to have a good reason.
As another example, the British set up vice-admiralty courts to try certain cases. These courts did not allow trial by jury. The colonists felt that this was being done to ensure that defendants would be convicted, regardless of the evidence against them.
Because of such actions on the part of the British, the founders thought that civil liberties were extremely important to guard against what we might now call a "police state."