The FBI contacted trust and safety and said 'Hey we have concerns about these tweets'. Twitter decided to take them down in some cases.
Who is corrupted here? Twitter for taking reports and then deciding how to react to them? The FBI for finding misinformation that might lead to crazies creating mass casualty events?
The FBI at no time FORCED twitter to do anything. So it's not violating the first amendment.
This is just an optimization and a way to save everybody a lot of time and headaches, as well as a way to ensure that the genie gets put back into the bottle before something can grow legs and do a lot of damage. And with the degree to which social media has been weaponized that is a good thing.