You don't need to be a terrorist to end up on watchlists. Read up on "Red Scare".

I know about the Red Scare. After reading about Venona project, the fact that most spies in 40s-50s were almost all communists I understand how the red scare came to be and support it.

The government comes after people left and right all the time who don’t do any of those things.

I’m conflicted here. I’m familiar enough with online “leftist” (especially of the supposed anti-colonial stripe) spaces to know how many bad, often highly illegal things are coordinated there. But I’m familiar enough with the FBI to know that their actual activities often consist of terrorizing political dissidents for no other reason than to neutralize their opinions. Without more information, it’s sensible to to default to innocent until proven guilty and push the FBI to justify themselves.

Give me 3 examples in the last 10 years of FBI terrorizing political dissidents to neutralize their opinion.

A decade ago the FBI heavily shifted its focus to CVE, countering violent extremism. At that time, the focus was on Muslims and groups that could be perceived as proxies for their interests (Anti-War protesters, pro-Palestinian groups). CVE relies on debunked theories about radicalization, and its definition of violent extremism includes peaceful, constitutionally-protected, political speech.

More recently, focus narrowed from violent extremism to RMVE, racially-motivated violent extremism, focusing on white supremacist groups--the definition of "white supremacist" being interpreted so broadly as to include explicitly anti-racist libertarian groups.

Given that the FBI officially considers "violent extremism" something to be extirpated, and defines it so broadly that the majority of the activity falling under that umbrella is legal political activity, I don't really see how you can possibly make the case that the FBI isn't trying to quash dissent. FBI raids have a chilling effect on political activity, they know this, and they use it.