Dude! Jehovah's Witnesses may not be making a living, but it is their job. They are called by God to perform this job. At least they believe so, and I respect their right to do it. (Just as I expect Sarah Brady to respect my right to keep and bear arms.) It's the law. They have a right to invite you to converse with them (unless you have posted your property as a no proselytizing zone).
It also is their right to protect themselves against dogs that are strangers to them. Your erstwhile guests did not know that your dogs are well-trained. How much sense does it make for you to take exception to them carrying pepper spray when you would not wish for them to take exception to you carrying a gun with you when you go to their church (supposing that you decide to check it out)?
They weren't carrying spray to hand out pamphlets. They were carrying spray to protect themselves. To object to their right to protect themselves while going about their calling is a little too close to the anti-gunners' desire to disarm me while going about my daily activities.
That isn't how it works.
If you come onto my property and pepper spray my dogs, you WILL be riding in the back of the sheriffs car to the pokey.
I resent the hell out of people that want to come onto my piece of land and try to tell me how to live. It just isn't happening.
The last bunch that came here wouldn't get out of the car. My Dobie can look straight into the drivers window of a passenger car. He wanted me to "put my dog up". Dammit wasn't barking or growling, just staring.
I told him we don't want any and be on your way. They left.