A recent DNA test showed by ancestry to be 100% North West European. In relative terms, Northwest Europe is actually a very
small geographical entity (irrespective of national borders), and the original gene pool (which 60% of
All North West Europeans share) is also actually quite small. Thus the indigenous British are not mongrel in any sense. Virtually all Europeans share some 'Celtic' ancestry, as well (not to mention 2-5 % Neanderthal ancestry.

). I'm also 8% Norwegian, but when you consider that nearly all Icelandic women had Irish female ancestry, (Vikings like Irish chicks

), you'll appreciate how closely related Europeans really are, despite evolved cultural and linguistic differences. Ivar the 'Boneless' may not have been as 'boneless' as his name would suggest
The Cross of St George is also used in Georgia, Russia, and elsewhere. It's fine, but as far as flags go, it's deeds and words that endow any emblem with respect and esteem.
Considering that England produced Shakespeare, Dickens, Jane Austen, Edward Jenner (of Vaccine fame), Darwin, umpteen nobel prizewinners, The Beatles, 'Stones, and many of the World's inventions I'd say that the English (and I'm a Scot) have an awful lot to be proud of.

Whether it's knuckle -draggers, or boffins waving their flag, I'd say they've a perfect right to be proud of it (and f**k the naysayers!!)
"Get your facts first, and then you can distort them as much as you please"- Mark Twain.