Should military service be a prerequisite for a student loan?

no. Why should only veterans be eligible for a loan at a lower interest rate that is subsidised by the taxpayers of the country, the vast, vast majority of which are not serving in the military or vets? It is in the long term interest of the nation to increase the education level of the population. College graduates as a group make significantly more over their lifetimes than high school graduates ( of course there are notable exceptions, but as a whole, it's a fact). Those who make more will pay more taxes which will more than repay any federal expenditures for the loans. Plus spending that additional income will contribute to a growing economy.

No. The BEOG, Pell Grants, and Student Loans should continue to be for students from lower income families to help them through college. We now have a very good GI bill for our active duty service members and if the current system is not broke why fix it?

Absolutely not. If service was a prerequisite, only a small percentage of potential students would be able to get a loan. This would deny an education to many people who need the loan.