From both my parent's ethnicities being reviled, to me being a weirdo, to my odd tastes in music, etc, I was ridiculed from 3rd grade until junior year HS. That last year I figured how to defend myself. And I did that by AGREEING with them.
Maybe it helps that I got sorta grim looks, but basically I tell them, "Yeah, I am, and? You got a problem with that? Good."
Ping pong wars, as seen on the web, "You're a troll!" vs "No I'm not, you're a bigger troll!" only succeeds in proving both idiots right. Anyways, it's just words. People take this stuff too seriously. Triggered, snowflake, butthurt - just words. Binary blips dancing on the electric sky.
Ignoring, walking away is very effective, because by not reacting, their need for reaction goes unfulfilled.
But in HS, due to what was going on back in my father's country at the time, I suddenly became public enemy #1. No one to turn to. Relatives lived far away, and my family always blamed me for getting picked on. So one day I got ticked off. And I've been ticked off ever since.
Even if it doesn't apply to me, I tell them that's what I am. What are they gonna do, not invite me to go bowling this Friday? Big whoop.
I'm not saying you should take that approach. I naturally look like an ugly thug plus I inherited a pair of angry looking eyes even when I'm not, and grew up in an family of constant squabbling, so I can get away with more that some others might.
My, "Go ahead, do it, like right NOW" works for me. Others, on the other hand, might get obliged.
I can also go on and on and have said things I later regretted. So restraint ain't such a bad thing.
But perhaps finding a way of saying, "Yeah, I am, so?" might work for you.
Regardless, people like that so-called friend do no matter. So therefore they make the loudest noise to prove they do. But they still don't.
Tomorrow will be another day, and you will find your stride.