Hey Pandas, Would You Stay Or Leave?

They do not deserve your loyalty, save it for someone who does.

I would leave, but with a final word. I would explain why I need boundaries and all the ways I had been loyal when they hadn't, and then I would politely ask them to change.
If they don't, I would walk out and find healthier friendships.

Unrelated, but after reading your title, "Should I Stay or Should I Go" from The Clash is stuck in my mind.

Unfortunately you have to cut toxic people out of your life

Omg. Leave. Leave leave leave. This happened to me twice because me and my friend decided to help the "outsiders" in our year at school feel like they had somewhere they were accepted. Me and my friend invited 3 people to be with us a couple of years back. 1 used us for attention by faking suicide over and over again. (He also used his mother's death to his advantage to get attention). The other was deeply depressed and wouldn't accept help from us and once tried to cut his wrists in front of me. And the 3rd was a racist, sexiest, homophobic and so much more and he didn't care that he made us all uncomfortable. Me and my mate have cut all 3 from our lives now and we see why they were originally alone. So yeah. Just back to the original two me and my mate.

My advice, leave as soon as you can. It makes you so much happier knowing you've dodged a bullet now that could've been a nuke in the future.

Why are you loyal to a fault to this person? Move on, there are millions of people on the planet.

Leave. This person isn't a true friend. I've always been one of life's misfits and when I was younger would do anything to try and fit in, to be one of the crowd. I would drop everything to help them and go out of my way to please them, but the second I needed a favour, no matter how small, they would run for the hills. After years of being routinely let down, hurt and humiliated I decided to ditch my fairweather friends and I don't regret it.