Removing iMessage from Mac

So I have gone through and disabled everything to do with iMessage on my Mac and iPhone, my macbook pro (2016)is running macOS Sierra v 10.12.3. when I open the app, all of my messages are still displayed, how do I remove them with out deleting them? if I delete them on my Mac is it going to remove them from my iPhone as well? My computer is password protected but sometimes I let may mom use it and I don't want someone to just be able to open iMessage and see everything. I have attached an image, this is after logging out of iCloud and disabling it on my mac and iPhone.