I don't mind a child trying anything to see if they like it - it's a good thing in my mind as it widens their taste experiences. Anyway, I always give just a small amount of whatever it is (teaspoonful for example) and if they like it then they can have more. If they don't then nothing's lost.
However, surely a 10 year old should finish a small amaretti (spelling?) biscuit, not eat half of it, try to put it back on the plate and then say he was going to put it in the bin as he didn't like it. I can understand that they're not to everyone's liking, but I think it's rude to just not finish what you've started to eat. It's not a very big biscuit, and I think the principle is to just eat something that you've started.
No big deal really, just wondered what anyone else thought?