@anyolddinosauryou make some fair points about not judging an entire faith by the actions of one individual and about distinguishing a kirpan from other knives.
Where I disagree is the claim that gurdwaras teach Sikhs to dislike Britain. That's a very broad accusation about thousands of gurdwaras and hundreds of thousands of British Sikhs. Criticising aspects of British colonial history is not the same thing as teaching hatred of Britain or British people.
British Sikhs have served in the armed forces, the NHS, public service, business and politics for generations. That doesn't suggest a community that is fundamentally opposed to Britain.
It's also possible to discuss policing failures without assuming they are caused by anti-racism training. If there were mistakes in this case, they should be examined on the evidence rather than fitted into a wider political narrative.
For me, the most important point remains the one you started with: a murderer is responsible for his crime. The actions of one man should not be used to condemn an entire faith community, and neither should they be used to justify broad claims about what all Sikhs are taught to believe.