Anyone running for a political office is, by nature, opening themselves up to a full examination of themselves, their background, their past and present associations, and their actions.  When certain aspects of this vetting process are questionable and explanations sought, the candidate must be ready, willing, and able to answer them in a satisfactory manner.
Only the totally uninformed cannot realize that there have been, time and time again, terrorist acts committed by Islamic radicals, acting alone or in groups under the influence and/or with the sanctions of terrorist organizations whose stated purpose is to destroy infidels in whatever ways possible.  If a candidate may have been associated with one of these organizations, questions should be asked.  In fact, the same should hold true of any candidate who may have been associated with any radical group that advocates violence and death to others.
When one chooses to be a public figure, it opens you up.  Stop whining!