He just gave his name as 'Death to traitors, freedom for Britain' in court so I think we can safely say he was using violence for political aims which is LITERALLY WHAT TERRORISM IS. And the reason it is actually important to be calling him a terrorist is that if a so-called Muslim (I say so-called because no real Muslim would commit an act of terrorism) had stabbed and shot a British MP and shouted 'Allahu akbar' (an equivalent to 'Britain First' I suppose) everyone would obviously label him as a terrorist. To be honest we just need consistency. Either we call everyone who commits acts of terrorism a terrorist, or we don't call anybody a terrorist. You can't pick and choose based on someone's ethnicity.