It's a shame that we even have to suggest this, but safety comes before religion and Jewish males in France are being targeted. Whatever god you believe in knows that you believe regardless of what you where or how often you go to church. You can't do good deeds if you're dead.
French Jewish males, or anyone for that matter, should not be urged to abstain from wearing anything. Unless there is a health issue involved, no person should tell another person how to live their life or how to express themselves. Expressing ourselves is one of the only universal freedoms most of us have, and it is one of the most important freedoms.
I think that if French Jewish males and French Jews in general should express themselves and their religion as they please. By following this suggestion, it would bring about comparisons to evading Nazis in World War II. Yes, it is a very dangerous time and area for them to be living, but it should be their decision based on their safety and welfare to make this decision and should not be urged by others not in their religion to express themselves differently.
Skullcaps or Kippas, as Jewish call them, are symbols of their religion. A recent attack on a French Jewish male, while disheartening, should not have us stray from our beliefs. I wish the hatred towards what others believe would stop, you need to realize that everyone has different beliefs and will not force them on you if you just let them be. Many people wear a crucifix to symbolize their belief in Christianity, and that would be like asking millions of people to not wear one so they aren't attacked. We must not fall to the "bullies", and stand for the strong, whatever your belief.