Roll over isn't the only alternative to lawyer. OP could always just say "no" and see what happens. Maybe lawyers come in to play eventually, maybe they don't.
See that's why you talk to a lawyer first. They could let you know what the possible forks of 'see what happens' are. There might be angles there that are detrimental to the OP and it would be good to be aware of those up front before doing things that can't be undone, such as saying 'no'.
* OP is in the wrong and employer can't afford to pursue further. OP loses a lot of reputation as word spreads.
* OP is in the wrong and employer can't afford to pursue now. Five years down the line, when Oracle acquires employer, OP is sued for five years of damages.
* OP is in the right, but employer's lawyer crafts a very intimidating and compelling legal letter. OP backs down, having blown the relationship with the lawyer, loses rights, and is fired two months later.
It's helpful to be able to say "no" with conviction if one is right, or not press an issue if one is wrong.