The 25-year-old Ivorian international, making just his second Premier League start of the season, did not cover himself in glory, as he gave referee Anthony Taylor no choice but to send him off six minutes after the break for a headbutt on Leeds defender Ezgjan Alioski.
This was the fifth red card an Arsenal player has received in the Premier League since Arteta took charge last December, at least two more than any other side.
Arteta felt let down by the former Lille forward after the game and did not mince words describing his conduct.
"It is unacceptable. Unacceptable. At this level you cannot do it," Arteta told BBC Radio 5 Live.
"Considering how early we got Pepe sent off we have to take it. I never like a draw but in the circumstances, it's a point. It is unacceptable.
"The first half there were two different periods. The game broke a bit, we started to give the ball away and led to them having the space to break. The second half it was a matter of defending well and staying patient and using the pace of our players in the space they were leaving."
Pepe’s red card means he is banned for Arsenal’s next three games against Wolves, Tottenham and Burnley.
