There is no statistical evidence that unmarried people are more likely than married people to fall into the sins you mentioned. Most adulteries, for examples, are performed by married people (by definition, at least one party to adultery must be married—if neither is married, the sin is fornication, not adultery—and commonly the other party is married also). The moral defects that lead some into molestations are found in both the married and unmarried; those defects do not arise out of the state of celibacy—nor out of the state of matrimony. Among Protestant ministers we find cases of marital infidelity and, yes, molestations. Your non-Catholic friends surely would not conclude that a married clergy therefore should be rejected.