Hi A.,
I don't know that I would call the teacher a "crackpot," but I might question her sensitivity. As a teacher, you well know that children learn at different rates, and in different manners. Your child may not have an interest yet in using a pen, pencil, crayon, or marker to write his name. However, perhaps he would be motivated to learn to write the first letter of his name with his finger in a plate of cholocate pudding? - or possibly shaving cream? Maybe he's more attracted to mud, or arranging sticks in the image of the letter of his first name. Maybe, if he likes candy (there's a big "if," right?), you could make a special candy game in which he could arrange the candies to cover your dotted letters. Later, he might need to go over your dotted letters with a pen (markers are usually the most interesting) before arranging the candies over his writing - and then, of course, he would get to eat the prize! The idea is to make it age appropriate and developmentally appropriate for him.
You are obviously too intelligent to allow this woman to bait you into pushing your son to write in an effort to have him reach a level that she deems necessary. He can, and most likely, will learn this task best if the lesson has the most important quality for a four year old - FUN!
I hope this is helpful - and that you and your son have lots of messy fun together!
S.