My step son had the same problem at the same age. We started making him clean his pooped underwear himself.. which he found disgusting. He would whine and act like he couldnt do it but we would make it wash them out in the toilet. We didnt act like it was a punishment but more like a fact of life "well, when you get something dirty and you make a mess.. it is your job to clean it." We didn't give into his whining or his helpless attitude.. we just stood by his side and told him how to clean them.
I don't think this is cruel or causes any psychological damage... it makes them independent and teaches a kid to clean themselfs and not to rely on mom or dad. I am a kindergarten teacher, I would never do something to "screw up" my child. I tried the other suggestions that the other moms had a nd even made a post on here. Nothing worked until we started making him clean himself and his underwear. It wasn't torture or punishment and we didn't sit there and say "ohh, you are so gross. clean up your poop, that's disgusting!"
Kids don;t start to think it is gross or weird when another classmate has accident until about the end of 1st grade or 2nd grade. But the other kids do recognize that so and so pees and poops their pants on a regular basis.