Completely free education privileges those who are born luckily intelligent (as opposed to luckily "male", or "straight" or "white" - the stereotypical categories we, incorrectly, use when discussing "privilege"
. It is a slap in the face to those who are, unfortunately, born with learning disabilities, or who are unintelligent, or whose career paths will be different - factory workers, electricians, retail assistants, etc. Whether you're born smart or dumb is just as arbitrary as whether you're born rich or poor. Both can be changed through hard work, but people, in both cases, start from different positions in the scale.
So long as education is free at the point of use to allow everyone to access education who needs it, and some of your future earnings are used to slowly pay back some of the debt, then I'm happy. And that is the present system. By making it completely free you're giving intelligent people an extra privilege that they would have gotten anyway if they'd chosen to do a lucrative (and therefore socially value-adding) degree to get them into a good job.
I find the idea of non-university goers paying their hard-earned taxes on privileged people quite wrong, both morally and economically. It creates an inefficient education sector, people making worse choices knowing they won't suffer financially from it, and it disadvantages, typically, people in working class professions. And it adds to the deficit.