K.,
My son is 7 and when he was in public school he had many classmates that would not eat any foods that looked different, they just refused to even try. I have seen a number of boys in his cub scout den throw a temper tantrum when offered new foods. I believe their behavior was more about parenting and where the child could gain a bit of control for himself.
My husband and I decided when our son was 4 that he had to try a little bit of every food on his plate and if he didn't like it he couldn't say it tastes icky, yucky, etc. We taught him to say "I don't care for this" in a polite tone of voice. A few times in the early stages of the process our son displayed temper tantrums and refusing to even try a new food - our tactic was to send him to bed without dinner - the next morning I made him an extra big breakfast and didn't say anything about the night before. When dinner came that evening and again he started to refuse a new food we reminded him of the consequences of his behavior. Within a couple of weeks he learned to try new things without making nasty faces or using impolite words. He even learned that he liked the new foods and started requesting specific recipes for dinner. His favorites are still pizza, hot dogs, and taco salad; but he also enjoys pork piccatta, chili, chicken parmigiana, etc.
Now, our son's grandparents love taking him to restaurants and out with their friends because he has wonderful manners, tries new things, and uses polite words when asked if he liked the foods.
I would definitely recommend reading the books the other mom suggested, because if your son is refusing to eat due to sensory issues then the trick we used with our son will most likely not work with yours. There may be other suggestions in the books that will work better with your son's temperament.
I just know our son, who is very stubborn, and we used this technique successfully. The catch though is we gave him other opportunities throughout the day to make decisions and take control. Picking out clothes to wear, choices within his chores (he picks the color of napkins each person receives when setting the table for dinner), which subject he wants to do first for homeschooling, etc.
Good luck with your son and let us know how it goes!
-C..