Histrionics broke out at a Senate immigration hearing this morning when Senator Patrick Leahy called on Republicans not to use the Boston bombings as a weapon in the immigration debate. “Last week, opponents began to exploit the Boston Marathon bombing,” Leahy said. “I urge restraint in that regard.”

Perhaps the most prominent Republican official to have drawn a link between the bombings and the immigration reform proposal is Senator Chuck Grassley. And so, at today’s hearing, Grassley offered some curious pushback to Leahy that tells us a lot about how some conservatives are approaching both debates. Yes, Grassley actually said this:

“When you proposed gun legislation, we did not accuse you of using the Newtown killings as an excuse,” Grassley said. “I think we’re taking advantage of an opportunity when once in 25 years we deal with immigration to make sure every base is covered.”

Really? Here’s what Grassley himself said back on January 30th, over a month after the shootings:

Although Newtown and Tucson are terrible tragedies, the deaths in Newtown should not be used to put forward every gun control measure that has been floating around for years.

What’s more, Senator Rand Paul and other Republicans have accused the Obama administration of using the families as “props” in the push for gun control.

To be clear, if conservatives want to seize on the Boston bombings to make a political argument about immigration reform, that’s not necessarily something we should automatically condemn, as some Dems are doing. As Jonathan Bernstein notes, we should respond to events with politics. Politics are everywhere and they are inescapable. If major, consequential, nationally riveting events aren’t supposed to trigger debate over how we should organize ourselves and solve our problems, what should trigger it?

For the reasons I outlined this morning, I don’t believe the Boston bombings tell us anything all that relevant about how we should approach immigration reform policy. But pointing that out isn’t the same as claiming there’s anything inherently wrong or inappropriate about trying to apply an event such as the Boston bombings to the current policy debate. Substantively rebutting the argument that the bombings tell us something about how we should approach the argument over the path to citizenship is not the same as condemning the act of making that argument.

Now, it’s true that in pointing to major events to justify a political argument, one can cross the line from legit policy argument into demagoguery. For the record, I don’t think Grassley has done that yet. He merely said the bombings should be part of the discussion as we seek to determine what’s wrong with our current immigration system. That’s not the same as claiming, as others have, that the Boston bombings show that we should end the immigration reform debate entirely.

Similarly, Obama and Democrats said the Newtown shootings should be part of a broader discussion over how to respond to, and reduce, gun violence.

Grassley, however, only seems to believe this is appropriate in the case where he thinks it will help his cause.

Greg Sargent writes The Plum Line blog, a reported opinion blog with a liberal slant -- what you might call “opinionated reporting” from the left.