From the psychological aspect, there are many people with implicit attitude, prejudice, cognitive distortion, etc. The common factor is that they are unwilling to consider the possibility that their belief may be wrong, and if someone isn't convinced of what they say, they will either rage or dismiss. The only way to stop them is, as far as I know, via social pressure. For illustration, please watch the movie 12 Angry Men.
Now, would doing such a thing violate freedom of thought? If they say "it's my right to not listen to you", then would it be wrong to keep asking them to provide logical arguments, regarding their explicit statement to not continuing the conversation?
Article 18: 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.
Article 19: Everyone has the right to freedom of opinion and expression; this right includes freedom to hold opinions without interference and to seek, receive and impart information and ideas through any media and regardless of frontiers.
The definitions of harassment and stalking, as in my understanding, involve the disrespect of the actor to the receiver's well-being (or happiness, or quality of life). However, in this case, the opposite is true: because the actor respects the receiver's well-being, therefore they have to do this. If they don't do this, then they are in fact not respect the receiver's well-being. Otherwise they wouldn't need to do this at all.
This photo can help illustrate this. The anti-mask protest is stopped by medical staffs.