Why would the government spend resources on spying on feminist groups and/or black people social clubs? They pose literally zero danger to the interests of the ruling class?

Respectfully, that take is naive as fuck. Considering the political climate then (and even now), it's not hard to see how groups of citizens banding together for collective actions can easily disrupt the gravy train of the money class. Look at how quickly shit gets done in places like France when they have a general strike.

A mass of citizens banding together will ALWAYS be a threat to the ruling class. Because the ruling class only rules as long as the population is willing to let them rule, because their rule requires the citizenry to enforce and uphold the system.

I don't even know where to begin with this one

We also have the Snowden revelations... They also snoop on regular "normal" citizens, non-citizens and about everyone.

And concerning the "why": I guess if your job is to spy on people, and you have a big budget available, you do just that. And it's "better" to do more surveillance, than to miss something. Ideally you'd do total surveillance. Only thing stopping that is law and maybe some supervisory board.

Nawww so innocent....

This was back in peak Racism/Anti women rights times, the simple fact they were in a group, talking to each other about god knows what was enough of a threat to these thin skinned assholes to warrant wasting money and time on this.

FBI Website: https://vault.fbi.gov/cointel-pro

Other Sources:

https://www.britannica.com/topic/COINTELPRO

https://www.npr.org/2006/01/18/5161811/cointelpro-and-the-history-of-domestic-spying