I have to say, that's not only very disappointing, but a rather pointless decision IMHO.
Having come from a GA background, I believe I am FAR more likely to have a takeoff or landing incident in a LSA than a slightly heavier GA aircraft (or a 900KG LSA for arguments sake).
Many modern LSA are built to fit in this arbitrary 600KG LSA Rule. To achieve the standard 2 Seat (Adults), 100HP, 4.5 hours fuel criteria, they have to be built by very light construction.
The 750KG (or pick a number, 1000kg) enables stronger gear, slightly thicker skins, more metal plates / bracing at joints, stronger spar. IE a stronger built aircraft design.
It appears most of the modern LSA (especially Factory Built) are 600KG MTOW, with stall speeds around 27-35KTs. This requires approaches around 40-55Kts to achieve your landing speed (around the 30KT-ish mark).
Not surprising a 15-20Kt gust on the typical summers flying day will have a lot more affect on that LSA on approach at 45Kts or about to touch down at 30Kts, than say a heavier aircraft approaching at 70kts and reducing to 45-60Kts for touchdown.
So my personal experience is, you are more likely to be involved in a takeoff or landing accident / incident in a 600KG LSA than a more solidly built 750KG (or 1000Kg LSA).
And before everyone says, they should go fly a GA plane then. I think many that have lost their medical, or that are required to jump through ridiculous hoops to renew their Class 2 will tell you why. Remember, in a couple of years time, perhaps it will be you that loses your Class 2, or requires 6 monthly medicals with specialists tests to keep it.
I've just been reading about some having to do expensive sleep apnoea? tests because they are considered at risk?, or was it because they had a neck size larger than 42. ???
Someone trying to create a regular income administering these pointless tests to give someone a Class 2 to fly their 2 seat, 800 Kg RV-XX.
In regard to the argument, you are more likely to survive a crash in a LSA because they have a stall speed of 45KTS or less, firstly, I'm sure there are plenty of 750KG aircraft out there with a stall speed of 45Kts or less, and I would also question whether you may have a better chance of surviving a crash in a more solidly built 900KG aircraft (particularly Cockpit) with a stall speed of 50KTs, rather than a very lightly built aircraft with a stall speed of 45KTs. (I don't have proof, just surmising based on some LSA accidents fatalities I've read).
Strangely though, The same people that cannot fly a 2 seat aircraft over 600KG, or those that have failed a Class 2 medical, can all drive on the open road a couple of meters off oncoming traffic in their 3500KG V8 4WD, with more likely casualties should they become suddenly incapacitated.
Many amateur pilots would still drive their cars on the road when feeling unwell, but would mostly likely decide not to fly that day.
I don't agree with their decision, or arguments against it. Stifling bureaucracy gone mad, yet again.
How the hell did PPLs manage to survive flying small 1-2 seater SE GA aircraft in the 50s, 60s, 70s, 80s, 90s without all this bureaucratic rubbish.