What to do about rippers

The best thing you can really do is prevent theives or anybody from finding out about your secret plants. then you've got to have a second plan in case anybody finds out, like an enclosed, locked chain link-fence box. and of course your dog or dogs in the backyards, and your good old firearm. it's kind of common sense man, just make it impossible for them to physically get to the plants

The advantages of guerilla growing, no one finds your grow site
For your backyard though, I'd just go with an enclosed wire box with a gate and lock!
There's no way anyone can get through it, and if they decide to get the boltcutters out, not only will it take them a while to cut a hole big enough to transport anything in and out of, but you'll hear it from your house aswell.
Failing an enclosed box, barbed wire on the top is pretty effective.