Of course you can help them, there are options other than violence. For example you can get a baby gate or a home without stairs. https://parent.guide/how-to-baby-proof-your-stairs/ Gates let them e.g. move around near the top of the stairs without risk of falling down. Desired, consensual gates, which the child deems helpful to the extent he has any opinion on the matter at all, aren't force. If the child specifically wants to play on/with the stairs, you can of course open the gate, put out a bunch of padding, and otherwise non-violently help him.