If he had been instrument trained, he might have kept 90 kts on in the turn and wiped them all out on the hillside.
Although I see what you mean, an instrument trained pilot wouldn't normally have placed himself in such a position in the first place. The accident you describe has all the trappings of a typical "sunday pilot" not checking the weather properly before setting off.
An instrument trained pilot (hopefully flying a fully instrument equpped machine of course!) would have climbed to a safe height (minimum sector altitude or whatever). Maintaining 90 kts would then have been the safest option.......
Shytorque has probably explained the best option for a non IF trained pilot inadvertently enterring IMC. Get back to basics - wings level, ball in the middle etc. If you are then able to manage a gentle turn under such conditions without getting your head in a spin, or the aircraft for that matter, turn towards the lowest ground in the area before descending.
Shytorque's last suggestion says it all -
8) Next time plan your flight so you KNOW your terrain and turn back a lot earlier before you get yourself killed.
- although you should add "check the en-route weather thoroughly and, if in doubt, don't set off unless you are sure you can make the whole flight under conditions for which you are competent.....