It's meant to be ironic, making the point that people don't really change. Not sure what would be offensive about it unless you were a proud descendant of the actual Philistines, and objected to the use, since the 1600s, of the term philistine (uncapitalized, as this one probably should have been) to mean an uncultured boor.
Giant [tree] logged long ago but not forgotten would have been better IMO.