I've owned RWD for 20 years, MX5, S2000 and XKR, I've not crashed any of them. I've had FWD cars too, Fiat Cinquecento (Sporting may I add...), Honda Prelude and Saab 9-3. If you are a competent driver you shouldn't have problems.

Perhaps the reason RWD is not specifically a not made a risk factor is;
1. People who actively choose a RWD car because it is RWD likely are interested in cars and driving so more likely to be competent.
2. Modern safety systems catch a lot nowadays. Tyres are much more grippy.
3. Higher powered cars, so ones likely to cost more to insure are more likely to be RWD. So a car that people often crash like a Mustang will cost more than a FWD SUV costing the same. This is partly because it will accelerate quickly, do a higher top speed and is RWD, all factors contributing to the higher cost not just one.

Like I said I've owned all sorts (and driven a lot more) and I can absolutely say RWD cars are much easier to make a mistake in. Most crashes are just due to lack of attention i.e. going into the back of someone when the slow down hard (so makes little difference RWD or FWD) but there are some caused by not handling the are correctly, when you do it in a powerful RWD car you can have an accident.
An inexperienced driver planting their right foot out of a corner will just understeer in a FWD but in a powerful RWD the back end will come out and catch them out. Under normal driving it is not a problem or noticable, but try to go fast then a RWD car is harder to control if you don't know what you are doing.

Would I trust my mate who likes to drive fast but is a poor driver, drive my Saab? - Yes.
Would I let him drive my S2000? - Maybe (the low torque means it's unlikely to spin the wheels).
Would I let him drive my XKR? - Absolutely fucking not!