Racing forwards coach Laurent Travers told French media that Williams had committed an "inexcusable error".
"It is quite logical when you do something inexcusable that there is sanction," said Travers. "There is no need to have a tirade over it. He made a mistake, we are human beings and sometimes we do stupid things."
His arrest was just the latest in a series of off-field misadventures that had affected the club in recent months.
Former All Black Dan Carter faces drink-driving charges after being pulled over in Paris last month, and Munster coach Anthony Foley collapsed and died in a Paris hotel room, on the eve of a Champions Cup clash between the two clubs.
"We have a series that I hope will end," said Travers, who also lamented the extra scrutiny Paris-based sports teams were subjected to by the public and media.
"We know, as you know, that in other disciplines, other sports and even in other Top 14 teams, things have happened and nothing has been written."
Travers mounted a half-hearted defence of Carter.
"I would like to know, among you, who never took his car after drinking three or four glasses of wine?" he quizzed the journalists.
"Of course, this is not good. One excuses nothing but it is also his private life."
New Zealand Rugby chief executive Steve Tew was less forgiving of Williams and Carter, who have both used social media to apologise for their actions.
"It's very disappointing for them and the club they now play for; and disappointing for rugby and the All Blacks," Tew said.
