That's just silly. I've been driving for five years and I've never been in a major accident (just a few small taps because of ice), and I almost NEVER drive with two hands. It's just not necessary for most normal driving tasks. Anyone with moderate dexterity can make a turn, change lanes, or even do a full reverse-direction Y-turn with just one hand. The issue is, of course, driving with the distraction of a conversation.
Then again, I think it's all situation. If I'm driving five hours back to my parent's house and I'm on I-70 through Ohio (long, flat, no turns) while there's very light traffic, then I'm not going to have any problem using my cell phone. If I'm driving through the hills of Pittsburgh on unfamiliar roads and random stop signs, then I'll wait until I'm somewhere familiar to deal with the phone. If I'm on the phone and there is suddenly a lot of traffic or the potential for a dangerous situation, I'll tell the person to hold on, place the phone down, and get myself into a safe situation before I use the phone again.
It's just common sense. This polarized "I hate all people who ever use cell phones in the car" nonsense doesn't help anyone. It's simply an availability bias - the only time you *notice* someone on a cell phone is when they do something stupid and put you in danger, so you assume that everyone who talks on a cell phone puts people in danger. You'll never notice me talking on a cell phone in my car because I never do it in dangerous situations and I'm competent enough to know when a situation warrants my full attention and when it'll be okay for me to hit the cruise control, stay within the lines, and call someone about something important.