McCain, wife of Sen. John McCain, took issue with Paltrow's recent comments about online bullying.
In a speech at the Code Conference in California on Tuesday, the actress said that Internet abuse can be "a very dehumanizing thing" that was "almost like" war.
McCain, whose husband was a prisoner of war, called Paltrow "a joke."
"Gweneth [sic] Paltrow is a joke. Her life is like taking bullets for a soldier. What a joke! My 2 sons serving in the military should talk to her," McCain tweeted Wednesday. "Perhaps Gweneth Paltrow should go out on patrol with some soldiers. Kind of like a Red Carpet in her mind I guess!"
Paltrow used the war comparison to describe how her celebrity friends sometimes feel about hateful and violent Internet attacks. One celeb pal, she said, received a comment from someone wanting to "rape and disembowel" her.
"You come across [online comments] about yourself and about your friends, and it's a very dehumanizing thing," Paltrow said. "It's almost like how, in war, you go through this bloody, dehumanizing thing, and then something is defined out of it. My hope is, as we get out of it, we'll reach the next level of conscience."
McCain followed up on her comments in a subsequent interview with HLN.
"I think it was an ignorant thing to say and certainly a selfish thing to say. ... It's Hollywood, I don't know what else to say."