Washington (CNN)Donald Trump on Friday vociferously -- and repeatedly -- defended his claims that a judge overseeing a lawsuit against Trump University is biased because of his Mexican heritage, pushing back against criticism that his objections are racist. Trump, pressed by CNN's Jake Tapper more than 20 times on whether he was invoking racism in his attacks on the judge, continued to point to his plans to build a wall between the U.S. and Mexico and renegotiate trade agreements between the two countries as justification and validation of his critiques. The presumptive GOP nominee said U.S. District Court Judge Gonzalo Curiel, a federal district judge in the Southern District of California, has made "rulings that people can't even believe." "He's proud of his his heritage. I respect him for that," Trump said, dismissing charges that his allegation was racist. "He's a Mexican. We're building a wall between here and Mexico." RELATED: Clinton: Trump deserves some blame for violence outside events At the end of a lengthy exchange, Tapper asked: "If you are saying he cannot do his job because of his race, is that not the definition of racism?" "No, I don't think so at all," Trump said. Trump first broached these waters in an interview with The Wall Street Journal published Thursday, in which he said Curiel, who was born in Indiana, had an "inherent conflict of interest" in the Trump University lawsuit. "If he was giving me a fair ruling, I wouldn't say that," Trump told Tapper, pointing again to Curiel's background. "I think that's why he's doing it." "I'm building a wall. I'm trying to keep business out of Mexico. Mexico's fine," Trump said. "He's of Mexican heritage, and he's very proud of it, as I am of where I come from." Trump again called for Curiel to recuse himself from the case. Last week, Curiel ordered parts of internal documents, including "playbooks" regarding running the enterprise, to be released as part of a lawsuit against Trump University. The documents were released in response to a request by The Washington Post. Trump also dismissed concerns raised by Hillary Clinton on Friday about his temperament when it comes to foreign policy. On Thursday, Clinton charged that Trump had "thin skin" and should not be entrusted with the U.S. military arsenal. "I don't have thin skin. I have very strong and very thick skin," Trump replied Friday. "I have a strong temperament. It's a very good temperament and it's a very in-control temperament, or I wouldn't have built this unbelievable company. I wouldn't have built all of the things I've been able to do in life." "You can't have that success without good temperament," Trump continued. "We have been taken advantage of by everybody. We have people with weak temperaments."