The author had tweeted '#beinfected' about Melania, causing a barrage of angry responses.
One Twitter user said: "You are one sick man," while another added: "Delete this, there are Americans dying."
Another reported the comment to Twitter Safety asking: "Is it okay to promote killing/hurting the First Lady?" while another user told him, "You are the virus, Rick. You sad little mongrel."
"Rick is enjoying his popularity among the Liberal Left who, like him, are also unhinged. He’s the kid no one ate lunch with," someone else commented.
Piers' tweet read: "You disgusting piece of [bleep]."
The controversial author is a national Republican political strategist who has written books including Everything Trump Touches Dies: A Republican Strategist Gets Real About The Worst President Ever.
Piers is known for wading into debates and getting his point across so it comes as no surprise he had something to say about Rick's comment.
Yesterday (March 18), he clashed with Chief Secretary to the Treasury Stephen Barclay on Good Morning Britain over the confusing coronavirus advice offered by the government.
Mr Barclay appeared via a video link as Piers grilled him after 79 year-old Stanley Johnson - himself in a high-risk category - said on Tuesday (March 17) on This Morning he'll "go to a pub if he needs to go to a pub".
His comments came less than 24 hours after his son, Boris Johnson, advised Brits to avoid pubs and other social venues.
Over 70s and others in high-risk categories should be practising social distancing.
Piers asked: "So all young people, 20-year-olds, 21-year-olds, 22-year-olds, watching this who want to go out to the pub tonight what is your advice? It’s a very simple thing that needs clarity?"
The exchange went on and on, but even Piers couldn't get to the bottom of what people should be doing.
In another news, Lord Alan Sugar has suggested Piers should be self-isolating after his co-presenter Susanna Reid stayed home due to her son having coronavirus symptoms.
Lord Sugar wrote: "If @susannareid100 may have corona passed on from her son, does it not follow that as she has been in contact with @piersmorgan, he should be in isolation also?"
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