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It's important to note that this is not what the report states: they actually dealt with nearly all complaints of discrimination equally badly. The most significant disciplinary cases were all of an antisemitic nature though (Ken Livingstone, Jackie Walker). The report claims that cases were dealt with more quickly when there were factional gains for HQ to be made, and that since 2018 when Jennie Formby (who doesn't share the same factional allegiances as McNichol etc.) was installed, there has been a significant improvement in the way that cases have been dealt with. As @Thick_Hollins states above, this is a good summary: https://labourlist.org/2020/04/internal-report-lays-bare-poor-handling-of-complaints-by-labour/
"I didn't try to understand this but here's my hot take anyway" is a strong opening gambit, respect.
The accusation is that the 'staffers' (or senior management, if you prefer to accurately represent the degree of power the people in question had) actively impeded the disciplinary process for those accused of antisemitism - i.e. they intentionally made it more difficult for the party to effectively deal with the issue - for their own political ends.