The link you posted is not relevant, as it involves harming people who threaten your safety, whereas this discussion seems to be focusing on harming people who are on your land.
I have no problem with harming people who threaten others safety.
If some guy is coming at you with a knife, you have no choice but to shoot him (unless of course you have some other, safer means of protecting yourself)
On a side note, has anyone ever seen the texas chainsaw massacre?
Technically the main characters (the victims) were trespassing, so does that mean leatherface was completely within his rights to hack them up with a chainsaw?