The image of a doctored €5 note with the slogan "house Irish first" has prompted a massive fury amongst social media users.
The photo of the bill with the offensive phrase was posted by Councillor Anthony Flynn on Twitter.
The North Inner City councillor said on social media: "What kind of sick person does this?"
And the tweet received a huge public response, with hundreds logging on to register their displeasure at the message contained on the note, the Irish Mirror reports.
One urged the "keyboard warriors" behind the message to "get a life," praising Cllr Flynn for his work with the homeless across Dublin.
"Solidarity Anthony, you are so right we need to take care of everyone's housing needs," wrote another onlooker.
A third added: "Fair play to you @AnthonyICHH You do more in a day to help the homeless than all of these keyboard warriors do in their entire lives.
"Xenophobia has no place in Ireland and those who think it does are willfully ignorant of the history of the Irish diaspora."
Cllr Flynn has long been an outspoken activist on homelessness, and a frequent critic of the Government's track record on the issue.
Last month, after a horror beating left residents of Dublin's East Wall terrified, he hit out at unacceptable" lack of response from gardai to the violence.
The following morning, on a visit to the area, the councillor says he saw no visible police presence and spoke to a Garda chief who told him gardai "weren't available to come into the area this morning".
"It's completely unacceptable that there wasn't a reaction from Gardai in terms of first of all a show of police presence, and second of all in regard to supporting the community," Cllr Flynn told the Irish Mirror.
"Gardai should have been on site this morning to allay or curtail anybody's fears. That didn't happen.
"I spoke with the chief, and unfortunately Gardai weren't available to come into the area this morning.
"To me, that says that we haven't got adequate resources in the area."
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