CLOSE PROX ACR-WDB COMMUTER-LTT ON PARALLEL APCH TO RWYS 25 AT LAX.

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SHIFTED FROM ILS 25L TO VISUAL 25R ON APCH TO LAX. COMMUTER VECTORED FROM S FOR VISUAL TO 25L. RECEIVED TCASII RA TO CLB AT APPROX 2500 FT. ALL RED EXCEPT 3 GREEN DOTS AT THE TOP; VISUAL PRESENTATION WENT FROM -300 FT RAPIDLY TO 0 FT; INITIATED CLB AND R TURN (SINCE TARGET WAS IN 8 O'CLOCK POS AND KNEW ACFT WAS BEING VECTORED IN FROM THE L). THOUGHT I MIGHT BE DSNDING ON TOP OF HIM. WAS WARNED BY LAX TWR THAT ACFT WAS TO R ON APCH TO N COMPLEX. THE ACFT ON APCH TO 25L HAD ME IN VISUAL CONTACT. DISCONTINUED CLB; REESTABLISHED DSCNT; SILENCED THE TCASII AS IT WAS VERY LOUD AND DISTRACTING. (VIOLATES THE SPIRIT OF THE STERILE COCKPIT.) HAD THE I.O. LOOK OUT L WINDOW; ADVISED THAT THERE WAS AN ACFT ON OUR L WING. I OBSERVED A COMMUTER ACFT FLYING FORMATION ON MY L WING; LESS THAN 2 WING LENGTHS AWAY; STEPPED UP 30 FT MAX. THIS WAS NOT A SAFE MANEUVER! CONTINUED APCH AND LANDED. THE SOFTWARE IN THE TCASII IS OBVIOUSLY IF/THEN. IT SHOULD ALSO TAKE INTO CONSIDERATION LOCATION AND ENVIRONMENT. IN OTHER WORDS; AN EXPERT SYS OR BETTER YET USE THE EXPERT SYS OF THE FLC. PUT A SHUTOFF BUTTON LIKE THE ALT ALERT. MY PRIMARY CONCERN WAS THE SFRA OVER LAX WHICH IS FULL OF VFR TFC; NOT EXPECTING AN AIRLINER COMING THROUGH AT 90 DEG TO THEIR DIRECTION OF FLT.