The opening line of the link made me shiver:
The person writing the article suffers from a serious economics handicap:
You should retort by saying: well, what should the wage ratio be 20:1? 2:1? 1:1? The arguer is almost implying that an hours of labour for a cleaner is “equal” to that of a senior lecturer. Point out the subjective theory of value in response here etc etc.
You should point out that the poorest people are better off by being in employment than not in employment as well.
There was a good article ealier on about the Christian justification for state/government intervention in free markets here: What belongs to Caesar. And some advice for arguing with someone who has socialist leanings here.
Writing “The mission of the university is to provide education first and foremost not to act as a charity to those that willingly cannot find a better employer” makes you sound cold and a bit vulgar. Perhaps you should highlight all the charitable things your university does (it does do charitable stuff, right?) in addition to enlightening the next generation of young people.