Threats and legitimate harassment are illegal in the US. No further action needed there. Just call the police if you're in danger. Platforms are legally obligated to work with the authorities and remove illegal content.
"Russian propagandists", is a partisan issue and definitely something that free speech should help protect. I'd say this strikes at the heart of the issue actually. People can accuse those they disagree with of being "Russian" or "bots" then get them censored. Free speech stops this from happening.
It's not. No party in the U.S., or in any country, supports propaganda from foreign powers, and there's not much debate whether it exists; evidence of their activities is deep and wide. The Russians wish it was partisan.
There may be debate over which things on the Internet are the products of Russian propaganda, but that's the nature of effective propaganda - only the crappy stuff is obvious, and the effective propagandists want everyone arguing with each other.
https://news.gallup.com/poll/237137/republicans-positive-rel...
That is the raw data.
Just as we already decided long ago, not long after drafting the Constitution and the Bill of Rights, when we determined that it was not OK to yell "fire" in a crowded theater, and that sharing state secrets with the enemy, while technically a form of "speech", was still treason.