I'm talking about five things he might say in the situation he describes here:
When I visit schools, students who were six, seven or eight years old when we marched [against the Iraq war] ask how they can change anything if up to two million demonstrators couldn't.
Owen doesn't let on how he answers that question, so I don't know whether or not in doing so he endorses a possible presupposition behind it: namely, that street demonstrations as big as this should suffice for securing change. In any event, here are three things directly relevant to the question that Owen could say in response to it if he were so minded.
(1) On a matter where opinion is very divided, it helps if you have a clear majority on your side, as those opposing the Iraq war did not.
(2) In a parliamentary democracy, it helps if, when the issue dividing opinion is put to the vote in parliament, the view which you support prevails, as opposition to going to war in Iraq did not.
(3) In a representative democracy street demonstrations, even when large, are not sovereign.
Two further points Owen could make, if he were interested in helping the young to understand the deep and wide division of opinion there was at the time Britain went to war against Saddam Hussein's regime, are these:
(4) The human cost of the Iraq war was indeed terrible, as Owen now emphasizes. Just for that reason, in speaking of costs it is necessary to explain, if you want others to appreciate what the arguments of the time were about, that those who supported the war were influenced in their thinking by a concern for what the costs might be of leaving Saddam in power. There is reason to think they would not have been small either. Simply to omit that consideration doesn't contribute to educating anybody.
(5) Likewise, to write as if, prospectively rather than retrospectively, the whole argument had only one side, only one set of conscientious reasons, fails to enlighten anyone on why the debate divided people as it did. But this is precisely what Owen Jones does in his peremptory discounting of the presence of 'humanitarian considerations' in favour of the war.
Keep on battling away, Owen. You may eventually succeed in persuading yourself that there was no moral case for the overthrow by US and British arms of a genocidal and fascistic regime. But even the bump of holiness won't enable you to help the young - let alone anyone else - to understand what the divisions of 2003 were about.