I don't know what year you're in but this is pretty standard policy--if you asked for a regrade, there's always a chance they'll mark it lower.

I'd say take your lowered mark, POLITELY (not passive-aggressively) ask what you can do to improve in the future (protip: don't whine and say 'why did my mark go downnnnn') and take that advice seriously. If you're in a major that requires writing lots of essays, you're going to hit major bumps along the way. I'm generally a ~3.7 student but I got hit with a C- last week for my term paper. Went to office hours, got advice (and an extension) because my TA's really wanted me to take this opportunity to learn and do well.

Also, if you love what you're learning, be prepared to face criticism. It hurts when someone shits on something you worked so hard for, but that's one of the hard parts about being in the humanities.