First of all, if you've read Marx's Manifesto you'll know Stalinism and Leninism veer dangerously from both Marx's economic and his moral ideologies. Secondly, profesed Christian nations are responsible for far more death and destruction throughout recorded history than either Muslims, Stalin or Lenin are.
Third, criticizing a child who doesn't know better for asking innocent questions is outrageously ignorant -- not the kind of thing most liberals here would condone at all, hence the backlash against it. Nobody from any liberal organization in the UK, which I know of, promote the idea that an innocent child can't ask questions.
I once remember being on a trip with my father when I asked him ''Daddy, why is that man brown?'' and he explained to me that when people come from hot countries their skin needs to mechanize itself against sunburn, and so a chemical called melanin is present in the skin in order to do that, and that this trait is passed on from parents to children.
He got admirable glances and the black man, who had previously scowled, had smiled at me when I responded ''Oh, okay. I want to have it too, then I won't get sunburned!''
That's a liberal approach. My mother, a bit of a traditionalist and authoritarian, probably would have clipped my ear and told me not to ask silly questions, a bit like the response of the teachers above who metaphorically clipped the young man's ear for asking an innocent question.
Nothing about good liberalism, as far as I can tell, rationales that overt political correctness is an acceptable substitute for genuine educational enlightenment towards a more understanding society. My father knew this, and I know this.