Don't know if I'd start my kid off with an M3 but I definitely wouldn't have a problem putting them in a BMW. I'd rather have them in something well made than some Prius that would disintegrate upon hitting a pebble.
If I felt the child could handle an M3, deserved it, and I had extra cash to blow I have to say I'd consider it. Regardless of how much care we take with our lives the sad truth is no one is guaranteed tomorrow, and I'd be just as devastated if my kid wrapped themselves around a tree, than if they were being perfectly safe and got T-Boned by a drunk driver.
Just my 2 cents.