Read other letters about this article
I also recommend reading The Gift of Fear by Gavin de Becker--he heads a security company, and writes on the utility of fear as an indicator for personal safety. That is, you already have an excellent, well-tuned ability to detect danger. It's that little voice inside your head that tells you when something's up; it's been honed by millions of years of running away from saber-toothed tigers and the like.
The problem is that most of the time, we walk around worrying about all the wrong stuff--Muslims, flesh-eating bacteria, the Rapture, take your pick--that we don't listen to that little voice. We wind up dismissing quite reasonable fears (the seedy guy on the elevator looks dangerous, those kids down the street are frightening) and sometimes wind up as victims as a result.
So you should definetly learn to defend yourself. You should also figure out how to stop fearing Muslim immigrants, because that kind of fear will blind you when your brain is actually trying to tell you something.
Disclosure: I do not receive any remuneration for recommending de Becker's book. It's really good!