Fox News Channel to Lindsay ... Here's Our Defense ... Cokehead Seems to Fit

Fox News Channel has responded to Lindsay Lohan's lawsuit over a comment a guest made about Lindsay and cocaine -- truth is a defense.

FNC has come out swinging, referring to LiLo this way: "Admitted cocaine user and long-time addict Lindsay ..."

You may recall, a guest on Sean Hannity's show said, "Lindsay Lohan's mom is doing cocaine with her." Lindsay and her mom sued FNC for defamation, but the network now says it has 3 sold defenses:

-- Sean didn't say it ... a guest did.

-- The network has a Constitutional right of free speech, without fear of lawsuits.

-- Lindsay's an admitted coke user.

And you may recall this ... Lindsay made a frantic call to her dad in 2012, which he recorded, in which she claimed she was being held hostage by Dina in a car, adding, "Mom's on coke."