I have had to become aggressive in enforcing my boundaries before from someone who wouldn't leave me alone, or that come to my door regardless of the No Solicitors sign clearly signaling my wish for privacy.
Maybe you have the wrong approach Paladin.
It seems to me that respected boundaries are more often crossed within the family. For example, do or do not children have a will to believe as they deem fit above and beyond what their parents wish them to believe? It often presents a challenge to both the parent and the child. Or between the roles of the husband and wife, male and female. It further becomes a problem in the religions of medicine, education, and state law. For example when someone allegedly needs help then others might point the finger and say 'you need help' and that the person needs to see a 'professional'. What exactly is a 'professional'? Would that be a person more knowledgeable in the arts involving the flesh, chemicals, psychiatric re-programming, or NLP? Or would that be the pastor or the priest? Would that be a 12-step program per the will of the individual, or would it be a state institution shoved against the will of the individual? That is where I see boundaries being crossed. Some not only share their advice like, 'You need laid'... but then feel the need to do something about it.
As a child, if someone comes to me with any beliefs whatsoever and insists that I must hear them... that person would be called a parent, a teacher, a doctor, a friend, or a neighbor. Some did more and insisted they had to prick my finger, give me shots, and make me turn my head and cough... is there a boundary to this 'professional' treatment? What if I don't want their 'professional' treatment? So it is not just the neighbor at the door, it is the family, the school, the church, and the capitol building down the road... each wanting to do something for me that I am not so sure I really want them to be doing for me.
For that reason if someone comes to my door and says, 'Hear me'... I'm going to listen... why? Because I'd much rather encourage that stranger to approach me with words than to approach me with terrorism, the state law, or some other method of mandatory coercion or 'professional' service. I'd much rather that individual find open doors willing to talk with them about their beliefs. For example if Ted Kazinski or Bin Laden showed up at my door then I would be absolutely ecstatic. What an opportunity. The door is open and I insist that they stay for dinner. Now I'm the one doing some insisting... come to my house and you can educate me all you wish about any belief or topic, but then I'll have words in exchange and the exchange will have an effect.
If I do get annoyed by the entrenched beliefs of a persistent neighbor then I'd do my best to reveal to them why, which can help develop what some here have called a cognitive dissonance. That alone could send them running. There are other methods though... most importantly: to give to them. The more that is given to the person who knocks on the door, the more they become disturbed because their purpose of knocking on the door in the first place was not to receive, but to give. So then have the dish already prepared and give to the person who comes to the door. I had a JW come to my door so I thanked him and I invited him in, and I offered him food, and I conversed a bit, but it wasn't a minute later the guy was making up reasons to leave. Y'all come back now.