The former England captain, making his 150th appearance for the club, was shown a straight red card for a late challenge on Isidoro. It was his fifth dismissal with Madrid and the eighth of his career.
Once again Madrid left the field to whistles from an angry crowd who have seen only one goal in four home league matches.
Madrid remain third with 42 points, one behind second-placed Sevilla who host Atletico Madrid on Sunday.
Leaders Barcelona, on 46 points, visit fourth-placed Valencia on Sunday.
In Saturday's late game, sixth-placed Real Zaragoza defeated Villarrael 1-0 thanks to a goal from Diego Milito.
Beckham and Brazilian Robinho started on the flanks against Betis, who knocked Madrid out of the King's Cup last month.
Although the home side dominated, chances were hard to come by. The hosts had keeper Iker Casillas
HOME ATTACK
Five minutes from halftime, a rare Betis attack led to Fabrice Pancrate going through on a one-on-one with Casillas, who got his hand to the midfielder's shot.
Raul joined Ruud van Nistelrooy in the home attack for the second half but little changed.
Beckham crossed low for Van Nistelrooy in the 63rd minute and the Dutchman's shot skimmed off the top of the crossbar.
Soon after, Betis defender Nano's shot from a corner cannoned off the far post and in the 75th minute Pancrate broke clear before shooting wide with only Casillas to beat.
Tempers flared towards the end and Beckham lost his cool after being dispossessed in the Betis area, chasing back and lunging into a challenge from behind on Isidoro.
Beckham only returned to the team last weekend after being banished to the stands by coach Fabio Capello following his decision to join Los Angeles Galaxy at the end of the season.
Betis are 14th in the table.
Reuters