Uhh no, you warn them before the manouvre because you had it planned in advance.
So you've had someone do something stupid and dangerous and afterwards noticed that they were on the phone, therefore all people who use a phone (even the ones you haven't noticed because they didn't do anything to draw your attention) must be stupid and dangerous.
I'll accept that the vast majority of phoner drivers these days are useless, but professional drivers (eg Police, HGV, taxi) have been using similar systems for years without problems. Admittedly two-way radio is a little different because both people involved in the conversation know that the main task is driving and therefore they keep it short, to the point and don't get offended if the driver doesn't give an immediate response. There's no reason that this can't apply to mobile phones. They're just more expensive and more complicated radios after all.
No if you read what I said, I said "I'd like to do..." not "I will do..." - two entirely different ways of phrasing the sentence.
No, you can't warn them before a manoeuvre - because sometimes you have to perform a manoeuvre quickly and instinctively. Maybe you have a larger brain capacity than me but when driving down a country road, I try and take in all the road surfaces, iron works, hedges, hidden exits/entrances, oncoming cars, cars behind me, bikes, people, and as many hazards on the road - doing that and talking, as well as feeling the car and controlling the car is too much for me to dedicate run time to all of it, it's either one or the other for me. I don't know how you're able to have an in depth conversation and be aware of everything around you... either you're not paying attention to the call (which as the caller I'd find most frustrating) or you're not paying attention the driving. Either way, even if you're only giving 70% on the driving, that's 30% too little IMO.
I admit and concur, that if I were driving at 20mph then I'd feel much more comfortable chatting on the phone, that is one point I will concede. However driving near the speed limit on a country road or the motorway (no matter how busy) requires some dedication to the actual task at hand, i.e. driving.
I think even "professional" drivers have little excuse for being on a phone/radio - and as such should keep it for emergencies or urgent situations - such as the police responding to a 999 call, or a crime in progress etc... furthermore a lot of traffic patrols have 2 officers in the car so the non driver can use the computer and make radio calls.
You may be a driving god with the brain capacity of 50 men (and possibly a woman seeing how stubborn you're being...) however I urge you not to have an in depth conversation on the phone in the car whilst driving... if you do, please don't be anywhere near me.
As you say, people drive badly enough as it is these days - giving them something else to distract them with is absolutely daft.