Would you be annoyed if an American/Canadian told you they of English and Scottish descent?

I recently asked if i could claim UK citizenship through descent and some prick told me "Don't tell people here that you are of English or Scottish descent, it is extremely annoying". Well naturally i couldn't help but be offended. The majority of my ancestors came from the british isles, all you have to do is look at my family tree and you will see names like Smith, Laing, Ellis, Quelch or Tetley along with many more. So anyway, why should someone be annoyed by that? I do declare sir! I have been insulted!