"Fudd" is a reference to the Warner Brothers cartoon character Elmer Fudd.
It is used as a pejorative to deride gun owners that, for some reason, think the 2nd Amendment protects their right to hunt and kill animals.
"Fudds" are the reason for almost every anti-gun law in the US, UK and Australia. Anti-gun people use "Fudds" to push their gun bans because "even gun owners agree" with whatever nonsense they're pushing.
For example, whenever you see me, or someone else, post a picture of a Short Barrel Shotgun, Short Barrel Rifle, Sound Suppressor, Machinegun or any gun that has a flashlight affixed to it, and someone questions the necessity or prudence of owning such things, all while purporting to, themselves, owning guns... that person is a "Fudd" and is an ENEMY TO THE US CONSTITUTION and a THREAT TO LIBERTY.
People like Chuck Schumer and Diane Feinstein are honest about their intentions. People like Wayne LaPierre and Jim Zumbo (and others on this and other gun forums) are not. These people "compromise" on gun laws and advocate banning guns that they don't own or like.