The son of Robert F. Kennedy has been arrested and charged with harassment and child endangerment after allegedly getting into an argument with nurses when he tried to take his newborn baby out of a hospital last month. According to police in Mt. Kisco, N.Y., Douglas Kennedy, 44, was arraigned Thursday. Kennedy and his wife, Molly, insisted the accusations are “totally false.” The nurse in charge of the unit, Anna Margaret Lane, said in a deposition that Kennedy said he wanted to take the baby outside “to get some fresh air,” despite protests from doctors and nurses. The doctor on call that night, a close family friend identified in court papers as Dr. Haydock, said he witnessed the incident himself and the charges are “incomprehensible” to him.