That's not true. The bill does not allow Facebook to "deem" any communication "malicious". It can share only indicators, a term that has a definition in the bill more detailed than that of any other computer security term anywhere else in US law.
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.