But it's far more offensive and far more vile to suggest that the State has any right to regulate public speech based on its content.
If you want to control what is said at the funeral, don't have the funeral in public. End of.
Why? Offensive to whom? There seems to be general agreement that some speech crosses lines that are not okay and should be regulated. This is why all countries that have freedom of speech protections also have a list of exceptions. In the US, certain things like ads, pornography, slander, sedition, and lies are generally not considered protected speech. It depends on the specifics in any given case, but I’m not offended at all by the suggestion that the State should be allowed to regulate these kinds of speech when they cause harm.
She was the head of state who presided over genocides, resisted the independence many dozens of British colonies, got carveouts in laws to shield her personal possessions from scrutiny for stolen antiquities...
I could go on.
Public figures in general, and heads of state in particular, lose the right to be treated as "just somebody's mom". They get treated by the public based, at least in part, on their treatment of the public.
And even apart from all that, this funeral, at a time when many, many UK residents are facing skyrocketing costs for everything from food to electricity to heat—as in, increases of 5-10x, not just a few percent—is projected to cost upwards of half a billion pounds, from what I've heard.
So no, let's not "say it is your mom's funeral".
Then it is pretty damning that not almost everyone is shouting! I'll go even further, then it is outrageous that people around the world mostly, including in the US, are saying what a great person she was.
So I wonder why is that?
Also, my understanding is that the person who got arrested for heckling was doing so because Andrew had sex with a 17 year old. So he was more upset about that than the queen overseeing genocides.
And if people really think she was evil, why wait until death? Why not speak up very loudly while the person is alive in order to affect change.
Weird priorities, or misdirection.
Having someone removed for being loud and obnoxious is a much different thing than being arrested and potentially incarcerated for same.
False equivalence.
This is the accession to the throne of a monarch wrapped around a funeral.
That doesn't happen when anyone else's mom dies.
And the people being arrested were in public places.
Funerals are reasonably often held at public cemeteries. FWIW I disagree the arrests were justifiable unless the protestors refused to be non-violently lead away from the scene, assuming they presented a genuine risk of provoking a violent response from the mourners etc.
Of course it would be wrong for the police to arrest people for being disrespectful in a cemetery. What would be alright is if the owners of that cemetery wanted them to leave the property, they refused, and the police were called. That's why all of the photos of Westboro protesting at funerals were them on the sidewalk facing a cemetery.
Just because City Hall is public doesn't mean that there aren't rules that you have to follow when you're there, or that you can't be kicked out when you break those rules. What it means is that you can't make up rules, because those are just the whims of the ruler.
If there are no rules at a publicly-owned cemetery against verbally abusing your recently dead mother in front of her grandchildren, you have to face that the abuser, as part of the public, has as much a right to be there as you do. But in real life there will be posted rules, just like there are rules at the public pool.
If Britain wants to pass a blanket law criminalizing all criticism of the royal family, they should. Plenty of dictatorships and monarchies already have lèse majesté laws, they can just copy them. They won't have to make up rules or improvise.
This is extremely compatible with Juche thought. Let's say that the Kim family is the mother of North Korea.
One person, probably not invited, makes a scene, shouts a bunch of stuff. Perhaps they have a mental illness, perhaps they had a grudge against your mom - she might have been a judge or a teacher.
Are you just going to ignore it? Would you expect some security to remove that person so that you and others can have a peaceful funeral?