Things like a strong and independent media, legal system, parliament and police force are crucial to democracy. It can be justifiable to argue that someone is anti-democratic if they advocate a narrative that erodes trust in any of these.

That's an interesting idea. Covers both political parties, with the left undermining trust in the police, and Supreme Court. The right in the FBI and journalism.

It's context-dependent, but that's the basic idea. In the UK for example, we currently have quite a right-wing government in power, which is:

* Undermining our Supreme Court by trying to force through a migrant deportation scheme which the court has ruled unlawful

* Eroding the Police Force's independence by claiming they are biased in their approach to protests

* Trying to defund and delegitimise the BBC

It might be because I'm fairly left wing myself, but I think you have go pretty far into authoritarian-left territory (think Stalinism) before you start becoming seriously anti-democratic. Before that point most leftists are pretty keen on giving power and choice to ordinary people and communities.