Why Should We Have Guns?

In the twentieth century, about 20 million people were killed by their own governments. This is an argumet that i've sort of kicked around iny d for libit. If it prevents enormous genisides or huge amounts of bloodshed every hundred years or so, then it may be worth it to have a low level amount of gun deaths over the course of time. I haven't seen anyby explore that argument, but it seems basically right to me.