Democratic presidential candidate Julian Castro on Sunday said he "absolutely" believes his brother, Rep. Joaquin Castro (D., Texas), was right to release the names of San Antonio donors to President Donald Trump's "campaign of hate."

Castro appeared on MSNBC's Kasie DC, where he was asked whether he still believes it was the "right thing" for his brother to tweet out a list of Trump's donors "at a time of heightened– frankly fear and violence, that this might make these people targets."

"Oh, absolutely. I'm very proud of my brother and my brother took what is publicly available information that newspapers, other publications regularly do about people who maxed out, made the maximum contribution to President Trump here in San Antonio and he put that forward as he said as a lament to say, ‘wow, just look,'" Castro said.

"I believe that my brother had every right to do that and people should know who was funding that campaign of hate," Castro continued. "I believe that's completely legitimate information and I think one of the reasons that Donald Trump tweeted at my brother is because he must be afraid that people are ashamed they gave to him or something."

Rep. Castro received backlash this past week after he tweeted out a list of the names and employers of 44 San Antonio donors to Trump's campaign. Trump's director of communications, Tim Murtaugh, said, "At the very least [Castro] is inviting harassment of these private citizens. At worst, he's encouraging violence."

Multiple reporters came to the defense of the Trump donors, including New York Times reporter Maggie Haberman, who called the tweet "dangerous.’ CNN reporter Andrew Kaczynski acknowledged the information was public, but said, "Just because this is public information doesn’t mean it’s the right thing for a congressman to do."

"Many of these people are retirees & private citizens and the congressman is setting them up for harassment," Kaczynski added.

"I don’t know who Joaquin Castro is other than the lesser brother of a failed presidential candidate (1%) who makes a fool of himself every time he opens his mouth," Trump tweeted. "Joaquin is not the man that his brother is, but his brother, according to most, is not much. Keep fighting Joaquin!"

I don’t know who Joaquin Castro is other than the lesser brother of a failed presidential candidate (1%) who makes a fool of himself every time he opens his mouth. Joaquin is not the man that his brother is, but his brother, according to most, is not much. Keep fighting Joaquin! — Donald J. Trump (@realDonaldTrump) August 8, 2019

The Washington Free Beacon previously reported earlier in the week that the list Castro shared included at least two donors who previously donated thousands of dollars to him.

One of them is William Greehey, a San Antonio energy executive who contributed at least $10,000 to Castro during his first two campaigns in 2011 and 2013, according to Federal Election Commission records. Greehey was targeted by Castro for contributing $5,600 to Trump this April. Also included on Castro's list was Wayne Harwell, who gave $1,000 to Castro in 2011 and has also contributed to Trump.

Harwell told Fox News he doesn't plan on donating to Castro ever again.

"I was also on a list of people that gave to Castro and if he dislikes me enough that he wants to put my name out there against Trump, I'm not going to give money to him," Harwell said. "Obviously Castro feels pretty strongly against me."