What does "called on it" mean?

Context:

Mr Fang, on the other hand, is an individual who is reported to have published research that was not his, and was reportedly called on it by Dr Xiao. He has conducted himself as a man seeking revenge at all costs and has tried to discredit Dr Xiao at every turn. One has to wonder if these claims of assault are real or imaginary. It makes no sense for a man of Dr Xiao's stature to hire some fools to punch Mr Fang and then return to China sometime later to be arrested. If he had hired someone for this task, wouldn't he have known that they were arrested prior to his return to China from Argentina and avoided arrest?? Dr Xiao is a brilliant man, and this reported assault attempt seems to be the work of a fool, not Dr Xiao.