In my country our threshold is significantly lower by the way - it's around a million, so bog standard houses get hit by it.
I think that inheritance taxes are wholly equivalent to wealth taxes, e.g. "you have a thing, I like that thing, give me that thing", and therefore morally wrong.
I could agree with them on the basis that the money were minimal and solely used for security e.g. police and military, it's an insurance policy against theft, the Government has a monopoly on force and that's better than warlords.
It's not used that way though, so I reject the premise.