If a muslim extremist blows up a building and kills people...?

it is generally accepted that the western world would see that those actions do not speak for the muslim people as a whole, however if an anti-muslim extremist (with a western background) somehow managed to blow up a building or site with thousands of deaths for example: mecca, would the muslim world see that the anti-muslim extremists actions do not speak for the rest of the western population or would they blame and characterise every western person as a terrorist against the muslim world.