Well, if people don't like it they will have the opportunity to elect a president that will undo those executive actions in 2016. A law enacted by congress is a lot harder to get passed (especially because of how utterly worthless the congress is nowadays) but is a lot more permanent. Executive action takes one signature to undo.
We went ten years from 1994 until 2004 with an assault weapons ban enacted by congress (that btw gun manufacturers got an opportunity to exempt their products from) and I'm pretty sure we didn't all become British or turn communist.
If people are so bent out of shape by this, I really don't have a lot of sympathy. They had the last 8 years to freely load up on as many ARs and 60 round clips as they wanted. I support the second ammendment, my family owns a fuckload of guns, but gunowners, give me a break, my twenty dollar bag of weed lands me in jail and you go to any store in town for an AR of your choice and walk around on the street flaunting it under total protection of the law. Guns are so loosely regulated compared to pretty much any other commerce out there and also have several extremely powerful lobbies that gaurantee nothing meaningful will ever be done as far as gun control I just really do not understand the paranoia.