People use them for mass shootings, but they also use pistols, and there's not a huge difference in the outcome.
Your proposed law would have very low effectiveness, but impact millions (maybe tens of millions) people who want to buy rifles.
Maybe you don't care about those people, but maybe that's part of the problem? They are fellow citizens, they can vote, and they have rights. And they know you don't care about them and they will resist your proposals because they don't trust you.
You can turn that around and say that they should care more about you, and maybe they should. But at some point, we have to communicate, because we (collectively) aren't making good policy any more.