Peter O'Mahony was laying on the ground with a perfect view as Tomás Lavanini hit Cian Healy recklessly with a shoulder an hour into Sunday's test match between Ireland and Argentina.
The Argentina second row was sent off for the third time in his career.
"He knew exactly what he's doing," O'Mahony said immediately after the cheap shot.
"That's scumbag stuff.
"Ah yeah, hard man. Good man, yourself. Hard man. Unlike you, isn’t it? That’s very unlike you."
Referee Matthew Carley subsequently called O'Mahony aside and reminded him that as captain he should "be an example" to other players.
Tomas Lavanini picks up the third red card of his Test career for this reckless hit on Cian Healy#IREvARG #rterugby
— RTÉ Rugby (@RTErugby) November 21, 2021
In the post-match press conference, with tempers cooled, O'Mahony had some sympathy for Lavanini.
Peter O'Mahony on Tomás Lavanini red card
"Ah look, it’s heat of the moment stuff," said O'Mahony.
"I’ve been on the other side of that as well so it’s a split-second decision from his point of view.
"These things happen. It’s split-second stuff for him. He’s trying to make an effort to clean someone out and he’s got it wrong.
"That’s what I thought at the time and you’re trying to look after your buddies, looking after your mates and the last thing you want is for them to get injured.
"From his point of view, it’s tough as well. It’s literally fractions of a second and at the time I was pissed off but I’ve been on the other side of it and you’re talking about hundredths of seconds where pictures change and, you know, red card.
"The disappointment of getting a red card for your country is nothing you can experience, I wouldn’t wish that on anyone."