It does seem an extraordinarily silly motion. Indeed asking what is "abortion culture" is a valid and sensible response.
And it's disingenuous of him to say it has no bearing on, and wasn't about , abortion rights. He is starting from the viewpoint that a legal act is inherently harmful to society at large. Compare the Scottish government's concern over binge drinking culture , a legal activity which harms and affects us all , and which concern has led to happy hours being banned.
Was he proposing that having established it was harmful that should be end of the matter? He would not turn it into an anti abortion debate?
I doubt Brendan O'Neill would have been the voice of reason so the whole debate looks as if it was contrariness just for the sake of contrariness.
The objectors however should not have been allowed to stop it. They could have attended and contributed although given the tenor of the quotes he selected I suspect they would have come out of it badly.