Clearly neither of you have any idea about how indoctrination and radicalisation work.
You only have to look at social media, politics, or religion to see that what someone 'knows is wrong' is entirely subjective and dependant on the sphere of influence they live in.
Many people think it's fine to bomb innocent people, as long as the intended target was an enemy combatant. Many people think the summary execution or imprisonment without trial of 'terrorists' is justified. Many people believe it would be morally right to hang a terrorisrt / murderer / rapist / paedophile / etc.
If you asked any mother of a 10-15 year old boy if they thought their son knew it was wrong to abuse women, the vast majority would say "yes, of course he knows how wrong that is". Yet, Andrew Tate and his brand of excessive / overt misogyny is built almost entirely on the backs of you boys/men and domestic violence / abuse is still sadly common place.
It's all well and good to say a 10-15 year old should know X is wrong, but that's wishful thinking at best, and reality is completely different. Without the right boundaries and checks in place (which people like Begum do not have) there's always a risk they'll not know X is seen as wrong, or be able to be convinced that X is acceptable in this situation or that situation.