They are basing that on this article [2].
[1] https://www.reddit.com/r/technology/comments/3q1kgl/facebook...
[2] https://www.emptywheel.net/2015/10/14/time-to-get-very-conce...
The first thing this bill allows for is to have Facebook rat out whatever communication they deem "malicious" to the federal government and be shielded from the fallout.
Meanwhile, the clear implication of the article we're commenting on, and the idea FFTF is trying to spread, is that CISA allows Facebook to violate user privacy, and to build its business doing so, by leveraging CISA. That's a nonsensical argument, and a terribly dishonest one.
CISA is a bad law, much more so than CISPA, which preceded it. The reason we have CISA instead of CISPA? FFTF.
I'm not opposed in principle to new investigative tools, but I don't think debate about them should be avoided by sticking them into cybersecurity bills.
Still: virtually everything organizations like FFTF say about CISA seems to be false, and all you have to do to see how is to read the actual text of the bill.