Well, is it?
I think it is ok and also important that any adult should feel able to tell any child to stop doing anything that is unsafe for themselves or others. A nice boy of 3 at our party was pushing others on the bouncy castle. His mother wasn't there.
I told him to stop pushing. He looked at me in complete confusion and said "you're not my mummy" then carried on pushing. Even at 3, he'd learnt, wrongly, that he answered to no-one except his own parents.