Always try the body blocking first of course but not always enough and particularly not with a dog determined to  get to your dogs  but I do agree that hitting a dog might cause it to respond with a bite. Rather be bitten than have my dogs attacked, sorry :-/
Are the dogs really attacking yours or just coming up to say hello? I have found so many people don't understand body language and jump in feet first to protect their dogs from what is percieved to be a threat but isn't. You must be very unlucky to have so many dogs wanting to attack yours, i have to say my experiences is that this is very few and far between, especially if yours are just minding their own business. Most dogs will run over, say hello and then go, very few run over to attack ime but maybe its something to do with different areas of the country? I would still say that kicking a dog that you percieve to be a threat may make it more likely to attack both you and your dogs and other people's in the future, just think of the psychological damage you could be doing to a dog that may simply just be an over exhuberant puppy.
Kicking a dog should only EVER be a last resort of the dog is physically attacking yours. But be prepared to get a lot of abuse from the dog and owner. Surely if you are having a problem with loose dogs attacking yours you would be better off carrying a spray corrector or umbrella to stop them in their tracks instead of a kick that could cause physical damage. 

Going back to CM, he doesn't protect dogs from being pts any more than otehr behaviourists, he just sets them up to react and then pretends to fix it. I wonder how many of these so called "red zone" dogs (one of his made up terms) actually are still fixed 3 years down the line? If they are truely that aggressive then it would take a lot longer to truely put the behaviour into extinction no matter what technique they use.