well, ISIS isn't getting young recruits from across the world from Buddhism, Christianity or Hinduism, no matter what the conspiracy theorists say. The Paris attackers weren't doing it for the glory of Buddha, Christ or Vishnu. If we can't acknowledge a problem, I don't think we'll be able to resolve it.
Much evil happens in the world - ISIS and Boko Haram are just two examples. Mass murder has happened elsewhere too, at the hands followers of other faiths. if God/Gods are all powerful and benevolent, why doesn't he/they stop this. Two reasons - either God/Gods aren't all powerful. Or, God/Gods are not benevolent, but malevolent entities who don't really care if innocent (such as the Yazidi women, or Syrian refugees or Parisian people) are harmed. In either case, not sure if he/they deserve to be worshipped. Of course, the third possibility is that there are no Gods in the first place - but I am sure this is not possible - so many holy men of different faiths attest to the presence of a higher being.