(trigger warning for a bunch of things, including rape and torture)

The Rotherham scandal is very well-documented on Wikipedia. There have been multiple independent reports, and I recommend reading this summary of one of the reports by the Guardian. This event is a good case study because it is easily verifiable; it's not just right-wing sources and tabloids here.

What we know:

Around 1,400 girls were sexually abused in Rotherham, many of them lower-class white girls, but also Pakistani girls
Most of the perpetrators were Muslim Pakistani men, though it seems like other Middle-Eastern and Roma men were also involved
The political and multiculturalist environment slowed down the reporting of this tragedy until eventually it got out

To substantiate that last claim, you can check out one of the independent reports from Rotherham's council website:

By far the majority of perpetrators were described as 'Asian' by victims, yet throughout the entire period, councillors did not engage directly with the Pakistani-heritage community to discuss how best they could jointly address the issue. Some councillors seemed to think it was a one-off problem, which they hoped would go away. Several staff described their nervousness about identifying the ethnic origins of perpetrators for fear of being thought racist; others remembered clear direction from their managers not to do so. ...

The issue of race, regardless of ethnic group, should be tackled as an absolute priority if it is known to be a significant factor in the criminal activity of organised abuse in any local community. There was little evidence of such action being taken in Rotherham in the earlier years. Councillors can play an effective role in this, especially those representing the communities in question, but only if they act as facilitators of communication rather than barriers to it. One senior officer suggested that some influential Pakistani-heritage councillors in Rotherham had acted as barriers...

In her 2006 report, she stated that 'it is believed by a number of workers that one of the difficulties that prevent this issue [CSE] being dealt with effectively is the ethnicity of the main perpetrators'.

She also reported in 2006 that young people in Rotherham believed at that time that the Police dared not act against Asian youths for fear of allegations of racism. This perception was echoed at the present time by some young people we met during the Inquiry, but was not supported by specific examples.

Several people interviewed expressed the general view that ethnic considerations had influenced the policy response of the Council and the Police, rather than in individual cases. One example was given by the Risky Business project Manager (1997- 2012) who reported that she was told not to refer to the ethnic origins of perpetrators when carrying out training. Other staff in children’s social care said that when writing reports on CSE cases, they were advised by their managers to be cautious about referring to the ethnicity of the perpetrators...

Issues of ethnicity related to child sexual exploitation have been discussed in other reports, including the Home Affairs Select Committee report, and the report of the Children’s Commissioner. Within the Council, we found no evidence of children’s social care staff being influenced by concerns about the ethnic origins of suspected perpetrators when dealing with individual child protection cases, including CSE. In the broader organisational context, however, there was a widespread perception that messages conveyed by some senior people in the Council and also the Police, were to 'downplay' the ethnic dimensions_ of CSE. Unsurprisingly, frontline staff appeared to be confused as to what they were supposed to say and do and what would be interpreted as 'racist'. From a political perspective, the approach of avoiding public discussion of the issues was ill judged.

And there you have it: concerns about racism hampered the investigation. Authorities encouraged a coverup of the ethnic dimensions of the problem. Of course, there were obviously other institutional failures here in addition to political correctness. This report is consistent with the mainstream media coverage. And this is the delicate, officially accepted report: I imagine that the true story is worse.

When a story is true, but it doesn't "make sense," that could be a sign that you are dealing with a corrupted map. I initially had the same reaction as you, that this can't be true. I think that's a very common reaction to have, the first time you encounter something that challenges the reigning political narratives. Yet upon further research, this event is not unusual or unprecedented. Following links on Wikipedia, we have the Rochdale sex gang, the Derby sex gang, the Oxford sex gang, the Bristol sex gang, and the Telford sex gang. These are all easily verifiable cases, and the perpetrators are usually people from Muslim immigrant backgrounds.

Sexual violence by Muslim immigrants is a serious social problem in the UK, and the multicultural political environment makes it hard to crack down on. Bad political ideas have real consequences which result in real people getting hurt at a large scale. These events represent a failure of the UK elites to protect rule of law. Since civilization is based on rule of law, this is a very serious problem.