It's a catchy argument, but it actually has a lot of problems.
1. Using this argument, we shouldn't ban anything because it's a "people problem" and not the product. Yet, we have bans and restrictions on tons of products. We have government agencies dedicated to the regulation of food, medicine, tobacco, etc.
2. We already ban certain types of guns/weapons because they are "too dangerous." Heck, just the mere act of bomb making is illegal.
3. This argument is really a side argument; it's a classic straw man. Instead of debating on whether certain laws should be passed, this argument wants to focus on the murderers/crimes. Notice that when this argument comes up, they abandon all reference to the actual issue. The two are actually two different issues. Or, think about it like cars. Cars don't kill people, people kill people. But, that doesn't mean we shouldn't have regulations on drivers nor have traffic laws.
4. People of this argument often like to say, "Any new laws only keeps guns away from law abiding citizens." Well, we all know that isn't true. See Orlando. Plus, using this argument, then we shouldn't have any laws.
More as they come.