It is unfortunate that the current system constitutes taking from the poor and giving to the rich, but this is justified as long as two things are true: first, overall, the government does redistribute wealth in such a way as to take from the rich and give to the poor, and second, the funding of universities from the public purse is of benefit to the poorer people in society. In this case publicly funding universities gives the poor the option of going to university that they would otherwise not have, even if they fail to take that option up. (The opposition arguments explain why this latter condition is the case.)