Bring on compulsory ADS-B!
A lot of gliders use FLARM units (a form of ADS-B) costing $1000 and now fitted to all gliders participating in competitions. You can't tell me it's not possible to produce a similar unit for GA aircraft at a similar cost, especially if there is a sudden demand to fit the entire fleet. Especially when I can buy a phone with gps and wireless for $200.
Car seatbelts are compulsory and have been for a number of years. Five seatbelts cost around $600 plus fitting, I'm sure there were the same group of whingers saying there's no need, just drive at a reasonable speed and don't hit anything. But now, nobody blinks an eyelid. Every new car is fitted with a seatbelt, every second hand car you get in to is fitted with seatbelts.
See and avoid combined with radio is a useful tool, but it has it's limitations, one being the human element. I've lost count of the number of radio calls I've heard from commercial pilots claiming "5nm north of the airfield" only to find them approaching from the south. If these are guys flying in GA for living, I dread to think how the weekend warriors go. Not to mention the ghost planes who manage to fly without a single radio call (wrong frequency?) We also have to realise the limitations of the human eye - there are now plenty of Kingairs, Conquests, PC12s, TBM850s, dropping in to airfields with groundspeeds up to 300kts combine that with a tiny ultralight or 152 and the time available to "see and avoid" each other becomes minimal at best (assuming no other distractions in the cockpit).
We all talk about the swiss cheese model. This incident illustrates how important it is to add another layer of swiss cheese, especially when there is a solution readily available.