"That (the criticism) didn't stop me from competing. That didn't stop me from being who I was," he said.
"It sure as hell didn't stop me from doing what I wanted to do in the past, and it won't stop me from what I want to do in the future.
He had asked to wrestle in the boys' division, but the rules for Texas public high schools require athletes to compete under the gender on their birth certificate.
Beggs entered the state tournament with a 32-0 record, beating three female wrestlers on his way to the championship.
"He has so much respect for all the girls he wrestles," Beggs' mother, Angela McNew, told AP. "People think Mack has been beating up on girls ... The girls he wrestles with, they are tough. It has more to do with skill and discipline than strength."
However, there has been a loud backlash from some sections of the wrestling community.
On Twitter, many commentators are saying it is unfair for an athlete who is taking testosterone to be competing in the female competition.
However, others on social media came to Beggs' defence after the booing video emerged online.
McNew would not make Beggs available for interviews ahead of the state meet.
The solitude allowed him to concentrate on the task ahead and perhaps shield him from attacks on social media and occasional insults from the stands — or even other wrestling mats — during meets.
Beggs' road to the championship last season included two forfeits in the regional tournament by wrestlers who feared injury. Beggs faced only one forfeit this season.
The opposing coach and teammates had insisted the girl wrestle Beggs, but she refused, McNew said.
Beggs' family has repeatedly said he wants to wrestle boys. The birth certificate rule was approved in 2016 by the University Interscholastic League, the governing body for Texas high school sports.
It was done to help schools determine competition, said Jamie Harrison, the UIL's deputy director.