Subtract the rhetoric, that there must be some further explanation, or that someone is lying.
It is a factual matter that four children were killed. It is a fact that they died due to an Israeli naval ship shelling them.
At best, Israeli armed forces were unable to identify the targets as children.
That makes them incompetent.
Or perhaps they deemed them collateral, however unfortunate, to some target in the area.
That makes them immoral.
At worst, they intentionally shelled a beach with no military target and possibly aimed specifically at whoever was running around, despite the targets being identifiable as children.
That makes them monsters.
There is no explanation that makes this fine, that justifies this. It would not matter if the Hamas strapped children to tanks. Use a weapon that is able to discriminate between targets better.