Bastareaud, 29, apologised after the match but will face disciplinary action and, if found guilty, would face a minimum ban of six weeks.
The incident occurred in the last minute of a 36-0 Toulon victory in which Bastareaud scored a try.
He tweeted: "I want to apologise for my reaction to the player's insults."
The centre, who has won 42 France caps, added: "I reacted badly in responding to his provocation, I'm sincerely saddened that I could have hurt people."