Well, what would
you do if the police executed a commando raid on your property looking for a meth lab that wasn't there, and your pets were slaughtered, but you really hadn't done anything to precipitate such events?
Given that context, it doesn't seem unreasonable.
Around the turn of the millennium, on my little software company's farm-like compound in rural California, we had a couple incidents where we would find one of our angora goats lying dead in front of the converted-barn office, with its throat slashed open from ear to ear. I happened across the first one when me and a buddy were out for a moonlight walk--after smoking a joint, no less--and it was some creepy fucking shit. I invested in a whole bunch of wireless night vision cameras after the second time that happened, and put them in trees, on the roof, and in the bushes.
It turned out it wasn't any kind of weird cult ritual or insane meth-heads living in the woods, as we had first thought; it was the German shepherd owned by the Nazi skinheads up the road, slipping its chain at night and going out on missions, apparently well-fed but still with the killing urge.
We didn't find out through the cameras; it was one morning when I ran outside at 5:30 after being awakened by the plaintive cries of our biggest billy goat, only to find him on his back with his neck clamped between the jaws of the dog (named Psycho (of course)). Luckily for me, those skinheads had apparently beaten a healthy fear of humans into the dog, so I was able to save Billy Whiskers by throwing some rocks and shouting.
Still, given the circumstances, it doesn't seem too paranoid to have planted all those cameras. If McAfee's story is true (which is admittedly pretty hard to believe) then going on the run, carrying guns, and deploying all the cameras and whatever else he can seems reasonable to me.