Can you give any example of this "preferential treatment" that people who aren't UK citizens supposedly receive?

(Cops doxx a man who burned the Koran) Manchester Police name Quran-burning suspect despite threat to life

https://freespeechunion.org/manchester-police-name-quran-bur...

Muslim abuser who 'didn't know' that sex with a girl of 13 was illegal is spared jail

https://www.dailymail.co.uk/news/article-2268395/Adil-Rashid...

Neither article specifies if either of these men are British citizens - I think you are trying to imply something, but I'm not quite sure what.