I'd go back and ask to speak to a manager. leave complaint too on Facebook if they have a page usually don't recommend people do that but places hate bad publicity. Very bad service

You actually let them kick you out? I've seen customers who are dead wrong to stand their ground on the issue and get what they want... you need to channel your inner witch lady.

Meant to put "white lady" and I tried to edit it to fix it about ten times but this stupid app is broken. FML

I liked it better when I did my own autocorrect of which lady to Witch lady (which in return makes me think bitch lady)... makes more sense because I've worked in retail and have seen all colours, shapes, and sizes throw tantrums towards customer service. and it could totally pertain to guys two because saying two feminine words in a row is like a double genderative and thus actually means masculine. obviously.

What happened to the shirt?

Did they keep it, or did you get it back with the tag still in it?

I would have broke it with a hammer.

If you break it, ink will pour out. Had to break one once, but wrapped everything in a plastic bag as to not get ink on it.
Sorry OP, should've stood your ground. Next time google ways to take it off yourself.

Shopping while black?

Sorry but I'm 90% sure this sounds exactly like an FML I've read before

That sucks, I had that happen with a pair of pants once a month after I bought them with no receipt and they removed it after the employee asked a couple questions. 

I'm going to speak for both sides on this FML
Customer- if you had your receipt then they should have taken off the security censer, they refused and threw you out you should have demanded to speak with a manager.
Store- A big scam that I have scene happen many times is buying an item and coming in with the receipt and Getting that same item and returning it. If this has been happening in that store they might have thought that what you were doing.
While the store is 100% wrong. They should ha

If you have a recipt, show it to them.

OP said that they showed to store their receipt. "...(even after I showed them the receipt)"

Absolutely call the store and speak with a manager. I've worked in retail since I was 16 and the golden rule is that you NEVER accuse a customer of stealing. If they actually thought you were trying to pull some sort of scam, they should have just called the manager over to begin with.

If the person accusing you was the manager  (since your FML doesn't state whether it was or just the cashier) then get the corporate number and file a complaint with a higher up.