you're explaining a clerical issue that lost a client a case caused by compatibility issue to other lawyers in a bar hgearing because your client sent you a document in a format that does not respect user freedom

they ask how you've managed to avoid this problem so far, and it turns out that you've been battling it nonstop for years

How do you justify that as a lawyer on the basis of "user freedom"?

Honestly your best defense is probably true ignorance or bad decision making that led you to choose something that, to non-developers, really only works as a way to save $100/yr or do some crazy new thing that didn't work. But that's still pretty bad.

Even if you're some crazy unix hacker wizard who for some reason works as a lawyer, how does never using Word help your client?