Many of Britain’s "leave" voters — who effectively voted Britain out of the European Union on June 23 — were motivated by a desire to slow immigration into the country. Now, they're taking those feelings out on immigrants already living there.

The Independent reported over 100 hate crimes following the referendum. Video taken in Manchester revealed white youths screaming "Get back to Africa!" A conservative politician told Sky News that "the atmosphere on the street is not good."

So, one American living in England proposed a simple symbol of hope: the safety pin.

"I'd like to come up with something that can be made by anybody anywhere to pin on their jacket or coat to signify that they are an ally," a young Londoner, who goes by Allison, tweeted on June 26. "…I quite like the idea of just putting a safety pin, empty of anything else, on your coat. A literal SAFETY pin!"

She later told British publication Indy100 that she chose the safety pin because it's cheap and easily accessible, and there were "no language or political slogans involved."

"It's just a little signal that shows people facing hate crimes that they're not alone and their right to be in the UK is supported," she said.

Allison kicked off the campaign with her own safety pin selfie.

Others quickly followed suit.

So far, there have been over 13,000 tweets about #safetypin.

Whole families are involved in the campaign.

Doctors embraced the pin as another way of serving the public.

And second-generation immigrants wore them in honor of their parents.

Some people even customized their pins.

They all want to transmit one simple message:

"You're safe around me."

Pin-wearers said they received heartfelt responses in grocery stores…

…and from deliverymen.

Some reported strangers being moved to tears by the display.

A number of UK immigrants tweeted their appreciation for the campaign.

But the action also drew criticism.

"Please don't wear a safety pin around me," Carl Anka tweeted June 29. "Don't try and say I'm safe around you in some meek effort to absolve you. I'm not here for that."

Anka and others argued that being a true ally against racism involves more than just good intentions — it involves listening, and occasionally acting. Allison responded with a tweet stream of her own, urging her fellow pin-wearers to take this criticism seriously.

"The #safetypin on its own means jack shit," she told followers. "What matters is what you do now that you've decided you wanna be a true-blue ally."

Allison suggested listening to those who are marginalized, without interrupting or claiming to understand how they feel. We say that’s a pretty good place to start — for Britons and Americans alike.