Earlier quoted context omitted.
That sounds like a spurious distinction. Pretty sure you can’t say “Person X is a murderer” and then say “well I’m only expressing my opinion, and in my opinion if you do something that annoys me that qualifies as murder.”
Nope, not in the US. It is perfectly legal to say, for example, "Kyle Rittenhouse is a murderer" despite him being acquitted. You're entirely free to disagree with the result, that is an opinion. Any opinion based on public knowledge is ok. It doesn't even have to be reasonable or rational. What you can't do is imply non-public knowledge, aka "I heard from my cousin who works in law enforcement that Kyle murdered a h…
That's ... not quite true. I wouldn't go that far.