We as yet have no idea what speed he was at when he impacted, nor what speed he did on previous laps or in general. THe problem with these conditions is again, one lap 200mph might be safe and another lap the same bit at 80mph can be unsafe and the ONLY way for a driver to know the safe speed is effectively trial and error.
It was ABSOLUTELY a safety car required to remove that car, not because of the corner, but because of the likelyhood in changing conditions of drivers not knowing the safe speed.
double yellows could imply slowing by 50kph(which is hard to implement considering 50kph less changes depending on where you are on the track) and he still may have aquaplaned off and hit that truck, he may have hit it less badly, he may have gone under the middle of the truck(had he arrived 1-2 seconds later).
There is a monumental difference between moving Sutil's car in the dry or full wet with everyone on full wet tires and moving that car in changing conditions where lap to lap different cars can do different speeds through there and require different tires.
Just because Merc/Red bull were fine on inter's doesn't mean the Williams(pretty crappy in such weather) and the Marussia didn't need wet tires. You can't in any way know you need to change tires until the inters become rubbish for you, you only find this out when going around on track. When rain increases in a race almost every car will be on the wrong tire for at least a lap, if not a few.
Putting any kind of recovery vehicle on track in changing conditions with a very high chance of another off in the same spot is insane, it needed a safety car to remove Sutil's car in those specific conditions. If they had to remove Sutil's car is another matter entirely.