The Cottagers defeated Liverpool 1-0 and ultimately survived the drop.
Benitez received stinging criticism from, among others, Warnock, then the manager of Sheffield United who went down.
Warnock - now at Crystal Palace - raised the issue again in a newspaper column on Saturday.
And Benitez said: "Somebody told me about these comments. We knew he was bad as a manager, prehistoric, but we didn't know he was a person like this.
"I will talk with my lawyers but we don't need to waste time with him."
The Spaniard continued: "Every manager has a responsibility for his team selections in every game and I also have a responsibility to use my squad.
"I picked a team I believed could win the match, We now need after this win just one more point to ensure fourth place in the league, even if Everton win all their remaining games.
"We've still got to be careful. We needed a good job done today and a good job was done.
"We can completely focus on Tuesday's Champions League game against Chelsea now.
"We've talked a lot about boardroom matters for a long time but for now I just want to speak about football, if that's possible.
"We've shown again we have quality and of course there will be some different players against Chelsea - but we can be confident."