That's not what we are talking about, are we?
That's the interesting question, I suppose.
When in the field service, I can recall more than one little set of eyes going very round when I as a publisher explained to the householder that the end of the world was coming (while Junior stood in the doorway). It never occurred to me what images I might be putting in this young mind.
When does preaching cross the line? Is it in content ("You're going to Hell", "You'll be destroyed at Armageddon", "Being dark-skinned is the Mark of Cain" [from our Mormon friends])? Is it in venue - from the street corner, on my doorstep, while representing my company?
I don't know that it is practical in the US to try to curtail evanglism, but I would support anyone making the choice to bar access to their property at least from religious expressions - I would think that, depending on circumstances, legal intervention (escort, harrasement suit, restraining order) may be appropriate to keep people away.
In all cases in the US, employers have the right and in many cases, perhaps, the obligation to prevent their employees from proselytizing while representing the employer (in uniform, on company time, using company assets).