Conservative groups lambasted Senate Majority Whip Dick Durbin (D., Ill.) after the lawmaker sent a letter to hundreds of alleged donors to the American Legislative Exchange Committee (ALEC) asking if they still supported ALEC and so-called "stand your ground" laws.

Durbin sent a letter to hundreds of suspected ALEC donors asking "whether companies that have funded ALEC’s operations in the past currently support ALEC and the model ‘stand your ground’ legislation."

"Have you no sense of decency?" the Goldwater Institute responded in a letter to Durbin echoing a famous question posed to Sen. Joseph McCarthy.

"It is the same question we pose to your office today in response to your effort to intimidate us for daring to associate with the free market, limited government organization known as the American Legislative Exchange Council," the Goldwater Institute continued.

The rest of the letter to Durbin from the Goldwater Institute reads:

Simply put, especially in the wake of IRS intimidation and harassment of conservative organizations, your inquisition is an outrage. We refuse to answer whether we are or ever have been a supporter of ALEC or its model legislation. We refuse to answer not because we disavow ALEC—far from it. We refuse to answer because as free Americans, that is our right. Your attempt to silence your fellow Americans through threats and intimidation because they don't share identical political beliefs is disgraceful and not worthy of the title you hold.

The libertarian Cato Institute also received a letter from Durbin and called the senator’s queries "a subtle but powerful form of government coercion."

"While Cato is not intimidated because we are a think tank—whose express mission is to speak publicly to influence the climate of ideas—from my experience as a private-sector CEO, I know that business leaders will now hesitate to exercise their constitutional rights for fear of regulatory retribution," Cato President John Allison wrote to Durbin.

"Your letter thus represents a blatant violation of our First Amendment rights to freedom of speech and to petition the government for a redress of grievances," Allison continued. "It is a continuation of the trend of the current administration and congressional leaders, such as yourself, to menace those who do not share your political beliefs—as evidenced by the multiple IRS abuses that have recently been exposed."

According to Roll Call, other companies among the 300 recipients include Anheuser-Busch, BP, Comcast, and Koch Industries.

Conservative lawmakers also assailed Durbin for alleged retaliation against political foes.

"Sen. Durbin’s request for ALEC supporters to announce an official position on gun laws in advance of a Senate judiciary subcommittee hearing is inappropriate, and I encourage recipients not to respond," Sen. Ted Cruz (R., Texas) said Friday. "In light of the current IRS targeting scandal, this action raises concerns about retaliation against those who may disagree with the chairman and the Obama administration."

ALEC is a private-public partnership of state legislators and businesses that works to advance free-market legislation.

While ALEC has written model "stand your ground" legislation, the organization says it played no part in Florida’s version of the law.

"Florida’s ‘stand your ground’ law was the basis for the American Legislative Exchange Council’s model legislation, not the other way around," the group said in a statement at the time.