This claim is true, as I was able to find the original source where the "Spanish judge" made these claims. It is important to note, though, that the phrasing of this claim is too extreme. The title of the Guardian article, from which this claim was pulled, reads: "Spanish judge calls for end to social media anonymity in hate crime cases." The judge did not seek to entirely "ban anonymity" on social media as is claimed above; he proposed identifying users who engage in hate speech/crimes on social media platforms-- which is a huge distinction to make and which I will explain further below.
This claim came from an article written by The Guardian, which covers American and international news for online, global audiences. It is a reader-funded news organization, with "no shareholder or billionaire owner," which allows free journalistic investigation without fear or pressures of favor (political, for example) and the ability to tell stories that need to be told (https://www.theguardian.com/about). So already, this claim is off to a decent start. It is important to note, though, that the article from which this claim comes is over a year old. It was written in August 2024, so it is a fairly less relevant story. With that said, I did find other sources that wrote and corroborated this story. But it has not advanced or been covered since 2024.
The Guardian does claim that after a stabbing of an 11-year-old boy in Spain, there was a wave of online disinformation that was spread about the immigration status of the perpetrator before there was any information out or arrests made. The attacker was not an immigrant but a Spanish man. Judge Miguel Angel Aguilar stated in response to this that purveyors of hate speech should be identified and social media platforms should be obliged to reveal users' identities in cases of hate crime. He believes this would change the climate around the spread of disinformation.
This story was similarly covered by Euractiv, an independent pan-European media network. Euractiv is, like The Guardian, funded by subscribers and thus does not lean towards or privilege one view above others. Euractiv is bound to the fulfillment of an "extensive list of criteria that to prove an ongoing commitment to transparency and solid journalistic ethics" (https://www.euractiv.com/about-euractiv/).
Euractiv's article (https://www.euractiv.com/news/spanish-prosecutors-step-up-hate-crime-probe-after-far-right-used-child-murder-to-falsely-blame-migrants/) confirmed the spread of disinformation in this case, as it explained that many people, "without any objective and verified data," claimed that African immigrants were behind the crime. This article noted that the perpetrator was indeed a 20-year-old Spanish man. The article goes on to share that Judge Miguel Angel Aguilar was interviewed by the private radio station Cadena SER. It was in this interview that he "proposed reforming the country's criminal code so that those convicted of committing hate crimes on social media... would be fully identified." Euractiv provided a link to this interview that can be found, in full, on Cadena SER's site. The summary of this interview, where quotes from Miguel Angel Aguilar are used, also contains an embedded link to the original interview so viewers can watch/hear it themselves. This makes it the primary source for this claim and the most concrete evidence for the claim: https://cadenaser.com/nacional/2024/08/21/terminar-con-el-anonimato-y-alejamiento-las-dos-propuestas-de-un-fiscal-que-lidera-la-persecucion-de-los-delitos-de-odio-en-redes-cadena-ser/.
Thus, it is quite true that Spanish judge Miguel Angel Aguilar proposed banning anonymity for social media users engaging in hate crimes-- but not for all social media users. This was proposed in the aftermath of a crime committed in Spain, where immigrant hate speech was spread with absolutely no evidence for it.
