Yes it invalidates your argument (unless you have a scientific study to support your claim). Leaving blanket statements that something is not only proven but proven to happen 100% of the time unchallenged leads to ill-conceived laws that target an activity 100% of the time, rather than focus on the real problem. MacNut and others (including myself) have pointed to the real problem: distracted drivers. The solution, have police cite anyone driving while distracted, no matter what the distraction is. Have the citation note why they were distracted. Make them go to traffic school and get lectured on the dangers of what they are doing and the consequences. If a driver shows a pattern of being distracted because of cell phone use, bar that person from using a cell phone while driving (do the same for any other identifiable distraction). Stamp it right on their license under restrictions right next to where "must wear corrective lenses" would show up. Then if they get caught again, move up to criminal charges or suspend their license. I guarantee that the message will get through.
Wouldn't they just lie about what was distracting them then? And how does that work against some distractions such as kids in the back seat?