The champions' victory denies leaders Real Madrid the chance to take the crown by simply beating Cadiz next Saturday. Los Blancos are 11 points clear of Barcelona with five matches remaining.
Williams spoke with the referee after hearing the alleged abuse when he was preparing to take a corner in the first half, and play was held momentarily as supporters were warned.
Turkish teenager Arda Guler's strike helped Real Madrid close in on the Spanish title with a 1-0 win at Real Sociedad on Friday, moving 14 points clear at the top of La Liga.
Laporta demanded the Spanish football federation and the refereeing committee send Barcelona all footage of the incident and audio recordings of the officials' conversations.
The coach was furious after Lamine Yamal had a shot which Barcelona said crossed the line not given as a goal after officials could not prove that it had using VAR.
The Catalan side have 68 points, seven ahead of Atletico Madrid, who visit Alaves on Sunday, and 10 clear of fifth-placed Athletic Bilbao, who drew 1-1 at home to Granada on Friday.
Barca moved to 70 points, eight behind leaders Real Madrid, whom they will face in the "El Clasico" at the Santiago Bernabeu next weekend.
Antoine Griezmann scored twice as Diego Simeone's men moved to within four points of their opponents and pulled five clear of fifth-placed Athletic Bilbao in the race for Champions League qualification.
"(Saul) entered the game well and scored a great goal," Simeone told Movistar.
Ideally, sports and politics should never mix, but inevitably, sports and politics always mix.
La Liga reported racist insults aimed at Vinicius Junior ahead of a league match last week at Getafe's stadium to Spanish prosecutors on Tuesday.
"(Atletico) are taller and they took advantage of that," noted Ancelotti.
Real Madrid coach Carlo Ancelotti said Saturday Barcelona complaints over his club allegedly influencing La Liga referees were unprofessional.
Barcelona earned a 3-1 win at Alaves in La Liga on Saturday with Brazilian teenager Vitor Roque scoring and then sent off in a lively appearance off the bench.
Spanish forward Joselu scored twice to give Real Madrid a 2-0 win at local rivals Getafe on Thursday, propelling them back to the LaLiga summit, two points ahead of surprise package Girona.
Atletico Madrid climbed third, above struggling champions Barcelona on goal difference, with a comfortable 2-0 win at home against Valencia.
Only a few months after lifting the Spanish title, Barcelona coach Xavi Hernandez dramatically announced he would walk away from the club at the end of the season.
Barcelona's title defence was derailed as Villarreal romped to a sensational 5-3 victory in La Liga on Saturday with three late goals.
Barcelona coach Xavi Hernandez said he will quit his "cruel and unpleasant" job at the end of the season after his struggling team were beaten 5-3 by Villarreal on Saturday in La Liga.