Hi 
Short(ish) answer.
Using Doc rather than DocX avoids a lot of fighting and awkwardness. Not all because "Save As ... " is too geeky for many MS users and they just can't cope.
Lengthy and tiresome answer ...
The professor probably has no control over what gets installed. That's more likely the job of the IT Department or external 'support'. That's why i suggested LO Portable. It's probably a bit awkward for them but they might like it if it doesn't scare them. He/she might prefer the non-ribbonised menus and the pretty icons.
The IT Departmen probably wont respond or do anything until they have had a load of students and staff pushing for it. So 1 letter is a good start but don't expect swift action.
The Student's Union are probably getting MS Office at drastically reduced rate so they wont understand the financial issue or the technical ones but might be a little sympathetic to the ethical issues. However, they might feel there are more important issues to address such as getting pens and paper cheaper or getting more funding.
IT Students and professors probably just use pirated MS products and/or get drastic reductions. They probably don't understand the ethical or moral issues. It could go either way but unlike many other students to IT people ...
global corporation driven by profits for corporate USA = good thing
For security and other issues IT students and professors probably believe that MS is best since it constantly releases security updates to patch on top of existing code instead of writing code that is secure and robust from the start, at all levels. Being reactive rather than pro-active means people notice results and activity.
People seldom realise the "Freedom of Speech" issue in all this, ie that FoS is only allowed after paying a rich global USA corporation for the privilege.
So, although there are ethical, moral, technical, security, financial and political reasons for preferring LibreOffice (and other OpenSource products) most people will only understand 1 set of those reasons.
So, stick to using the older MS format, Doc rather than DocX as the fastest way of getting the homework done.
Regards from
Tom 