The French league leaders had already had Marco Veratti sent off by the time Beckham received his marching orders, and two players were dismissed after the final whistle.
PSG started the game confidently but didn't really test the hosts until Zlatan Ibrahimovic's close-range shot was saved after 20 minutes.
Five minutes into the second half, they got their goal after an excellent move involving Veratti and Pastore allowed the latter to fire in from the edge of the box.
Veratti then hit the crossbar with a curling shot, before being sent off for a late tackle. Then just as he was about the be replaced, Beckham was also shown a red card for a high challenge.