That's the dilemma....I certainly don't have sound switched on (my dialogue could be construed as aggressive towards other motorists) and I also notice that I tend to drive more considerately when the dash cam is running.
So it can be used to moderate your driving style but also as you say, it can condemn in the event of an accident where it is your word against theirs.
You don't have to forward to footage to insurance companies though but in the clear-cut case of the other motorist being at fault then it's a definite 'must have' driving accessory.