I would have been very unhappy about that, at 2 years old. But on the other hand, when I sent ds1 to playschool I fould he was having what I thought to be a distressing amount of sweet stodge poured down his gullet - his key worker reported to me "He would taste the jam sandwich he had for lunch so he hasn't eaten much" (why the fuck did she think jam sandwiches were an appropriate lunch for a child who would happily eat egg, cheese or any meat?) and I 'registered my disapproval' by asking her to let me know when she intended to give out a lunch based on sweet food and I would provide an alternative he would be happier to eat.
Perhaps you could do the same? Give the nursery some chocolate buttons to hand over when the other children are being fed mad lumps of coloured sugar?