I don't seem to have issues with my betta and my ghost shrimp. I actually have a problem with the ghost shrimp smacking the bettas around if they get to food that the shrimp has already scoped out. Mine will literally jump all over the bettas to get the food back. I have 1 male gorami betta and 2 female betta and my 2 ghost shrimp are completely fearless and will stand their ground.
I do however have an issue with my male betta picking on my golden mystery snail. He will pick at his antenna and badger him until he hides for a few hours.
I do not mean to pry, but you don't by any chance happen to have six fingers on your right hand?