UN Declaration of Human Rights
Everyone has the right to freedom of thought, conscience and religion; this right includes freedom to change his religion or belief, and freedom, either alone or in community with others and in public or private, to manifest his religion or belief in teaching, practice, worship and observance
Everyone who believes in a belief, religion or something which involves them is allowed to spread and believe in it. No matter what it is, no one has a right to stop them from doing so.
A scenario where article 18 has happened was when world war 2 happened. This was because Hitler did not allow Jewish people to believe in what they wanted to believe in. In result, Hitler killed every Jew so the religion can't spread