Ah yes, let's pretend you can't tell someone is from south Asia or Caucasian.
First of all, you previously included the Middle East. And yes, I would not be able to determine ethnicity with certainty given the significant variation. Would you define Jason Mantzoukas as Caucasian? https://www.youtube.com/watch?v=6JtamJmtc0g
Its not about the way people look, its about their belief, Islam prohibits very seriously about blasphemy and that's why even the intelligent people can not help but comply. The same is not true about other religions.