not familiar with handling bladed weapons; (2) the attack is telegraphed and travelling at a tremendously slow velocity; (3) you already got hit before you have performed a disarming move on your opponent. If one of these three things is not true, then I'm sorry to say that either you would lose a limb, get severely wounded, or die in battle.
People who say that as civilians, you should fight to disarm, is I think disillusioned from watching too many martial arts flicks or has either already signed your death warrant. Out in the street, against a crazed lunatic who is out to kill you and take everything you have with him, you need not be overly concerned with your assailants' welfare. The important thing is first and foremost, to survive the encounter.
If one is only concerned with disarming a bladed weapon from an assailant when attacked, he would be only fighting at half his maximum potential. An individual would be aiming to control two things here: (1) to get out unscathed and (2) not to severely harm his opponent. As a victim, you have every right to protect your life and the life of those you are protecting.
If someone successfully disarmed an opponent from his weapon, then well and good. But if the opponent is not knocked out yet, you cannot be complacent that he wouldn't still have a go at you. There are many factors to consider in weapon disarming and if one still has not honed his skills to its full potential, he shouldn't be concerned too much about disarming. As a beginner, one is stupid to spend hours and hours of fancy disarming drills and techniques in a martial arts class where the feeder is travelling in slow motion while you, the receiver, on the other hand is barely moving at blinding speed using your best effort. You are wasting your time for something that won't work. Always remember that like any other normal empty-handed attack, a bladed weapon can change direction, strike, lock/trap, and take you down if need be. The myth of bladed weapon disarming seems to be a reality with most Arnis and Eskrima classes all over the world today. If this is your cup of tea, then expect your fingers do the walking when the blade sings its tune.