So, someone is quietly sunbathing in the corner of a field I own, but am not using at the moment. I spot him, and call in security. When they tell him to leave, he says, "Hey, I'm just having a little nap in the sun! I'm not hurting anything -- I'll be gone in a half hour."
Security goes to drag him away, and when he struggles, hit him on the head with clubs.
Now, surely, I wouldn't go so far in the "strawman" arguments against libertarianism that people keep accusing me of making as to contend that any libertarian would say that the sunbather had "initiated violence" against me and that I was just responding in "self defense," would I? No one could really hold a position that stupid, so what would motivate me to make up crap like that?
Well, I don't have to, because Geoffrey Allan Plouche did it for me:
"Throwing out trespassers who refuse to leave is not initiating physical force. It is retaliatory physical force. Defensive."
And, by the way, I think private property in land is generally speaking a good idea. But it's not some "natural right" -- it's a social invention, and governed by the norms of the societies that created it. In the UK, the sunbather would have every right to stay where he was, because the UK has "right to wander" laws. In the US, the police should remove him if asked -- because what he is doing is against the law, not because it is "initiating violence."
(Now, some idiot is going to come along and say, "So, Gene thinks it is OK to turn Jews in to the Nazis because that was the law." Just wait for it.)