I think you goofed.
Having figured out where this was likely leading, I would have drafted a resignation letter, giving two weeks notice and clearly explaining why I was leaving, and gone to the meeting anyway. If, in the meeting, they were trying to pin under-performance on me I would reply with the circumstances. If things got nasty I would hand over my letter.
Years ago I was the kitchen manager and brewmaster at a brewpub in Idaho. One night my boss took a swing at me across the bar. I went home and drafted my letter. Next morning he wanted to talk to me about my "conduct". Idiot came to MY office instead of making me go to his. Anyway, as soon as it became clear he was going to be a dick (incidentally the name he went by) I handed him the letter.
I've also just walked off jobs before but, handing a letter of resignation to someone clearly not expecting it is exhilarating and freeing. More so than just walking away. Many of the times I've walked a small part of me felt like a failure. Delivering a letter of resignation puts the power back in my hands.