There is no love lost between the Celtic punk rock band the Dropkick Murphys and Republicans in Wisconsin.

The Massachusetts-based band, which is vocally pro-union, got upset over the weekend when Wisconsin Gov. Scott Walker used one of its most popular songs, "I'm Shipping Up to Boston" as intro music for his speech at the Iowa Freedom Summit Saturday.

So this was their response:

The band's reaction isn't too much of a surprise. Walker effectively ended collective bargaining for unionized public workers in Wisconsin a few years ago. During the debate, the band wrote a song dedicated to Wisconsin unions called "Take 'Em Down," the Milwaukee Journal Sentinel notes.

Another top Wisconsin Republican, then-Assembly Speaker Jeff Fitzgerald, used the same song at the state Republican Party Convention in 2012, and the band criticized him at the time for the same reason.

By the way, Walker got high marks from several political pundits for his speech in Iowa Saturday – he was one of several potential 2016 presidential candidates who appeared there.

On Monday, the Dropkick Murphys issued a statement on their Facebook page explaining their reaction. It read, in part:

 "When a politician uses our music to walk out to, for better or worse, it brands us with that person. ... We feel that we have the right to ask to not be associated with certain events or people - we don't think that's too much to ask. This isn't a legal issue to us—we're not looking to sue someone. Yes, our words were a little harsh, but it was borne out of frustration with the past history of Wisconsin Republicans, such as Jeff Fitzgerald, using our music."

No comment yet from Walker or from the organizers of the weekend event in Iowa.

Still, the band's original tweet got a lot of reaction, both positive and negative, on Twitter. Here's a sample.

Here's a video of the band performing "I'm Shipping Up to Boston."