Uh-Oh
Do you want to know something else that grinds our gears? The way some people treat employees poorly is because they don’t know just how valuable they are. Here’s some food for thought, folks—don’t piss off the designer. You might end up royally screwing up.
This designer was kind enough to let their boss renegotiate the work contract, but we don’t think the OP would want to work under someone so inconsiderate and condescending. It’s best just to let HR handle the problem, but we get the feeling the boss would’ve just hit the Ignore button.