Dangerous Play fouls can be called before an event to avoid a potential collision e.g. a defender runs/layouts in a way that an accident would occur if the offence were to continue. When this occurs it is correct to not make a play on the disc & to call a 'dangerous play' foul.
Players calling a Dangerous Play foul before a potential incident need to have reasonable grounds for doing so. They should actually be able to see the on coming player and have some reason to believe that player will not avoid contact -- this could include a previous history of that player to not avoid contact. You cannot call dangerous play if you feel you could have made a play on the disc, but that would have resulted in you initiating contact. In that instance, you should just refrain from making the play.