I don't agree that's the correct way to describe what happened, I was basically "there" and part of it all. So many of us used hate speech, hardened SDS and naive high schoolers both and everyone in the "movement' inbetween. I.E., we called Johnson and Nixon baby killers, we called cops "pigs", we talked about revolution and "taking it to the streets", we didn't think twice about throwing stones in response to tear gas, most speakers at protests were full of passionate anger and hate at the government, we thought of those who tore apart the 68 Democratic convention as heroes and compatriots, we went to meetings where we watched films on how wonderful the Vietcong's fight was against our pig government, we sold Red Star Express on the street corner that called for the overthrow of government to support those meetings, we thought an honor to get arrested at a protest.  Etc.

Things grew worse and worse after Kent State. It was AFTER THAT, when nothing changed but got worse with the surveillance, that some of the more radical types like the Weathermen turned to a higher level of violence and more secretive planning.

 I started at UW Madison a year after the bombing of Sterling Hall. And truth be told, a year after that, no one I knew was glad that Fassnacht was killed and 3 other injured, but neither was anyone I knew unhappy about the strike at Dow Chemical. It was more like "collateral damage". I dare say some out of state freshman I knew chose UW precisely because that was where the action was, that was where the bombing happened. The majority hated those geeks with their crewcuts  across the campus researching weaponry and they hated us back.

Had I been there contemporaneous with the 4 bombers, they sound just like some of the guys I went on dates with a couple years later. They weren't that odd, they were common enough types that did it. And therefore I could have useful intel if I was being surveilled.

You have to infiltrate to get intel about planning of possible actions, they have to spy, that's just the way preventive action with angry groups works. The majority in them are not given to planning violent action but those planning violent action usually hang with a much larger sympathetic crowd.

Just the same thing these days, when jihadi types end up hanging with and talking with a much larger radically conservative Islamic population that isn't planning violence, like a mosque with a Wahhabi imam. They are all just hating, some end up violent. You can either surveil or you can limit the kinds of weaponry available. Those are your choices for prevention. 

Prosecuting after the fact isn't preventive action.

But doing all this, this is where you end up with the problem of entrapment, the infiltrators basically inciting violence. And eventually if not checked, a state like the GDR, where everyone is watching everyone else...

So were you unhappy about them infiltrating the KKK as well? Because that bigger picture is what I am talking about here: surveillance by law enforcement of groups angry about society in order to prevent violent action.If you want them to surveil all the white suprematist kids on 8 chan, next up could be a black separatist online group.

For example Is this symbolic hate speech or a real threat of real violence?

 chants like "The Revolution has come, it's time to pick up the gun. Off the pigs!",[50] helped create the Panthers' reputation as a violent organization. ~ Wikipedia entry on Black Panther Party

I actually remember seeing people chant that one. How is a low-paid not-a-mind-reading-rocket-scientist, law enforcement officer supposed to know at the time this kind of speech is just starting to gain traction?

Would you support law enforcement checking out and surveilling the activity of everyone in the Charlottesville march that chanted Jews will not replace us or not? There is actually no hint of threat of physical action in those words. Or just the ones that got into actual physical altercations that are actually against the law?