Greetings!
The bottom line is that it would be extremely unlikely to prevent a DC from happening - when it has happened in the past it was usually the Government that took such action, sometimes due to pressure from religious leaders. That wouldn't happen in the U.S. or many democratic countries.
Part of the question is whether the facility is a public facility or a private facility. If it is a public facility the Government/Local Municipality etc. would be hard pressed to deny JWs the use of the facility if they have allowed the use of it by other groups, or else it would face a valid claim of discrimination/violation of Civil Rights, etc.
A Privately owned facility may have more leeway in picking and choosing who they will rent the facilities to and might be more pursuaded by a campaign.
this statement from the Society's District Convention manual was interesting....
There is no need to talk about the delegates bringing their own food to eat at noon. This can cause local merchants and others to become alerted to matters not their business.
I think that it would be a surprise to the surrounding merchants, including the Hotels from the hotel list, to learn that the Society considers it none of their business that the thousands of delegates have been officially instructed to ignore them and bring their own lunch.
Whether such merchants have any influence over the facility owner is a question.
-Eduardo