European Professional Club Rugby (EPCR) condemned the Munster fan who confronted Saracens' Billy Vunipola at the end of the province's Heineken Champions Cup defeat at the Ricoh Arena.
Vunipola defended and 'liked' an Instagram post published by Israel Folau midweek in which the Australia full-back made homophobic remarks.
Folau said that "hell awaits" homosexuals in comments that resulted in Rugby Australia stating they intend to terminate his contract, effectively ruling him out of this autumn's Rugby World Cup.
In an apparent show of support to his fellow Christian, Vunipola stated that "Man was made for woman to pro create that was the goal no?"
He was booed by the travelling Munster support throughout Saturday's last-four showdown, and after the final whistle a man entered the pitch to gesticulate angrily at the 26-year-old.
A spokesperson for European Professional Club Rugby said: "EPCR does not condone the entry of a spectator to the field of play. Following the regrettable incident at the Ricoh Arena, the spectator in question is currently being detained by the stadium authorities."
Vunipola stood by his remarks after helping Sarries to an impressive victory.
"Behind closed doors I felt a lot of love, a lot of kindness shown to me," said the England international said as he collected his man-of-the-match award.
"I am just very grateful to be part of this team. From my point of view, I believe in what I believe in. There was no intention to hurt anyone. I am just grateful to play."
A final against Leinster or Toulouse awaits for Saracens as the English outfit target a third Champions Cup title in four seasons.
Vunipola added on BT Sport: "It is important we enjoy tonight, we will look to the final when it comes. We are back here next week and hopefully we can put out a performance we can be proud of.
"I am just excited as everyone else to watch tomorrow. Toulouse are an awesome team, they surprised a lot of people by beating Racing but we weren't surprised.
"We know what Leinster bring. They have flair, structure and world-class players, so we look forward to playing another final and are just thankful to be there."
