On the surface it might seem to be an easy answer...however there are always two sides to an issue (and sometimes three:). Following are some points I gleaned from debate.org. 

For:

• Education is vital and maybe the source for hope in the future
• Education improves humanity and preserves the planet
• There is still more technology and discoveries to be made

Against

• People won't value a free education
• Free education will cause havoc
• Who would pay for all the expenses

BTW, Many states already subsidize college and universities for free or with a very low tuition fee.