I really do think that they honestly believe things will be safer without guns. Over time, they think that guns will become less and less common, and we will not need to fear violence from those with firearms.
The problem is that they aren't thinking things all the way through. They'll end up having to do like the UK... beginning with gun crime, then knife crime, then bat crime, etc.
They're trying to make it impossible to break the law and harm others by focusing on the tools. If they remove the tools of violence from society, then there won't be violence, right?
Unfortunately, they have ignored the fact that some people are just going to be criminal and violent, and they will use anything to harm others. Take the guns away (even if you can keep them from such people), they'll use knives, table legs, a sock filled with change, whatever. Even their fists. Because that's what they are... violent. Removing the tools of violence from them does not change their nature and it does not render them safe to be out in society.
The question I ask: "Let's take a person who is in a frame of mind to go out and murder innocent children with a gun. Let's assume you can take that gun away and keep the guns away from that person. Is that person who honestly wanted to kill children now someone you want out and about... they don't have a gun, but that's the only thing that is different. Is that person safe?"
If the answer is "no," then it isn't the tool. But the people favoring bans aren't thinking that far ahead. They're thinking "well, we can maybe save a few... not all, but a few." Any lives saved are a legitimate exchange for rights they see as unnecessary.