That’s like asking if it’s really a murderer’s fault for pulling the trigger of a gun manufactured by someone else. Yes, it absolutely is their fault and no, “if they didn’t, someone else would” is not a valid moral excuse, ever.
Who is the murderer in this analogy? To me it's the government misusing such a tool.
Palantir. The government is the gun manufacturer collecting all the needed data in various places.
Why though? Palantir isn't the one using the tools for ill. The government is collecting the information and using it, possibly, to violate civil liberties and constitutional rights.
What can Palantir do to you?
Any other company with enough developers and data scientists can do what Palantir does. It's the massive amount of information their software uses that is the concern. But that data is collected by our government, and so we have legal recourse to it, either under current law or by passing new privacy laws.