Tigggys AIBU was simply asking if she was wrong to say no to ice-cream. Most posters have said she wasn't.
It was Tiggys DH that told his DD to use her knife. It was Tiggys DH that told his DD she couldn't have ice cream after she said she was full. Tiggy says she would have been given ice cream later, if she hadn't then thrown a tantrum, broken a glass pane in her bedroom door. Tiggys DH then told his DD (in the morning) that there would be no ice cream at all after she took some anyway.
But despite this, Tiggy has been told she is 'horrible' 'uncaring', that she should be 'teaching' a 10 year old to use her knife properly (not the child's mum or dad, but the step mother), that the child is obviously uncared for, unhappy, neglected and so on.
No wonder OP has lost her rag. The thread is rude, insulting and unfair.
This is a classic "step-parent" thread. Tiggy was going to be in the wrong no matter what she said. One poster (that I am very confused by on this thread) even states that someone agreeing with the OP "must have stepchildren" - because of course, only another 'wicked stepmother' could be in agreement.
The classic Passive Agression, sarcasm and wide eyed innocence from some posters is taunting and goading the OP into a response. It works and is used all the time. Then those posters get to pat themselves on the back on a job well done...and move onto the next thread doing the same.
I'm astounded that so many other posters can't see it and instead jump in and join in with gusto.