Looking at the statute again (§466), I think what the General Assembly was trying to accomplish with the law was to basically detach the automatic premise liability that applies to business properties. Think of it this way, if a person were being ejected from Delaware park for being disorderly and because they were flailing about, a greater degree of force was needed to escort them from the premises, but unbeknownst to the staff escorting the person out, they had a health disorder that made them more prone to physical injury, the defense of property section is there to absolve liability. Though there is a reasonable use of force to eject the person, the person could still sue for damages sustained as a result of the health condition. This is the so called "egg shell plaintiff" scenario. What §466 does is say that there is no claim upon which relief can be granted because the injury was the result of the lawful use of force in protection property interests.
I don't know that to for sure be the legislative intent, but from a legal and logical standpoint, that's the conclusion that I come to.