Declaring war with McDonalds

Okay here's the back story:

1- Out with James for our one year (we made it!), caught a cab home, saw the shinning golden arches and thought why the hell not?
2- I've been a strict vegetarian for over two years.

LC- Hi, can I please order a small cheeseburger meal, without meat, and an apple pie?
MD- No meat?
LC- That's correct
•time passes•
MD- small cheeseburger, no pattie?
LC- Great! Is there an apple pie too?
MD- I forgot. That's an extra $2.40
LC- Wow, that's expensive! They used to be $1!
MD- They went up (no shit, Sherlock)
LC- Do I get my drink too?
MD- Oh yeah. (If sober, I would have been a bit more sus by this point. But I was hungry)

So eventually I joined James outside, ripped the burger in half and took one big jumbo bite, forgetting to chew and swallowed the baby. (If you've seen me eat drunk before I'm sure you're imagining this acurately.)

You can guess the rest. The premise was there from the beginning.

LC- So yeah, my cheeseburger had meat in it. I'm a vegetarian.
MD- Sorry about that. I'll get you another.
LC- Are you the manager?
MD nods
LC- Do you have any idea how big a deal this is?
MD- I understand, I'm a vegetarian too. Have a medium fries.

The next part of the story is pretty embarrassing, I'll skim over it but basically involved a lot of tears and trying to make myself vomit and failing.

Here's the point of all this.

1- If I was going to return to the meat, it would never come from McDonalds.
2- Those frozen processed offal beef patties taste like arsehole. Serously. Have a break for a few months and when you try one you'll never want one again.
3- I don't want free stuff from McDonalds (James' first idea).

So I need your advice. Do I sue them? Write an angry email? Storm their restaurants? Or admit no self respecting human should go there for food in the first place and cut my losses?

Sigh. Two years to waste it on a fucking cheeseburger. It's like ending Dry July on a goon bag. I feel so cheated.