Yes it is disrespectful. It is always disrespectful unless you are for some reason absolutely unable as in physical ailment. At no point is civil disobedience "not disrespectful", because that's the point of civil disobedience; disrespect for the central authority and the established norms as a means of demanding change.
If you aren't saying it for personal reasons, then no. It's a form of silent rebellion, much like the famous and respected Martin Luther King's reaction to the civil rights movement. Silent rebellion. Some people viewed a black person sitting at a white bar disrespectful in its time, but Martain Luther King changed that. I do not say the pledge because I view it as a form of silent rebellion for removal of "one nation under God."