We see Kingsley use his Patronus to deliver the message that the Ministry has fallen. The Patronus just appeared in the middle of the wedding without any invitation.
The question is whether someone could stop a Patronus message from appearing to them? Like in the case of people sending hate mail and other vulgar obscenities over Patronus to other people.
According to the FAQ of some iteration of JKRowling.com:
Members of the Order use their Patronuses to communicate with each other. They are the only wizards who know how to use their spirit guardians in this way and they have been taught to do so by Dumbledore (he invented this method of communication). The Patronus is an immensely efficient messenger for several reasons: it is an anti-Dark Arts device, which makes it highly resilient to interference from Dark wizards; it is not hindered by physical barriers; each Patronus is unique and distinctive, so that there is never any doubt which Order member has sent it; nobody else can conjure another person's Patronus, so there is no danger of false messages being passed between Order members; nothing conspicuous needs to be carried by the Order member to create a Patronus.
This implies that a sufficiently skillful and prepared wizard could stop a Patronus. However, you probably wouldn't need to be on alert for spam or offensive Patronuses because only the Order of the Phoenix knows how to cast talking ones and it would likely be very obvious who did it if it did happen.
Nothing is ever mentioned about being able to stop a Patronus appearing to you, even if it was the bearer of bad news (i.e Kingsley), but we do know that Wizards with questionable morals rarely use the spell.
While there is a widespread and justified belief that a wizard who is not pure of heart cannot produce a successful Patronus (the most famous example of the spell backfiring is that of the Dark wizard Raczidian, who was devoured by maggots), a rare few witches and wizards of questionable morals have succeeded in producing the Charm (Dolores Umbridge, for example, is able to conjure a cat Patronus to protect herself from Dementors). It may be that a true and confident belief in the rightness of one’s actions can supply the necessary happiness. However, most such men and women, who become desensitised to the effects of the Dark creatures with whom they may ally themselves, regard the Patronus as an unnecessary spell to have in their arsenal.
- Patronus - Pottermore
(Highlighting is mine). I would say that since many wizards never saw a need for blocking others Patronuses, it never became a thing. So I do believe if a Wizard were able to believe enough in the message of hate they were placing in their Patronus, you would have no way of stopping it.
I'm not sure whether to post this as an answer, as it is primarily speculation, but it seems likely that if someone really wanted to stop a Patronus, they could. If one were in a location protected by the Fidelius charm and the sender had not had the secret revealed to them, then they would not know where to send the Patronus charm.
In fact, the sender simply being ignorant of one's location, without any magic blocking that knowledge, is likely sufficient. It's not hard to imagine that Kingsley knew that there would be a lot of OotP members at the wedding, and that he specifically sent it there, rather than his Patronus finding them on its own. Snape sent his Patronus to Harry only after learning his location:
Carefully examining the text shows that Hermione had her beaded bag open when she told Harry where they had stopped. Phineas Nigellus's portrait inside it overheard Hermione and reported that to Snape. Snape thus knows that Harry and Hermione are in the Forest of Dean
There isn't much reason specifically to think that warding charms keep Patronuses out, but there's not much reason to think they don't, either. Believing that they don't would require believing in some special exception for which no evidence is given.
The Patronus just appeared in the middle of the wedding without any invitation.
The Patronus itself may not have had an invitation, but it's reasonable to think that Kingsley had an invitation.
