Former Virginia Lt. Gov.  Justin Fairfax  rallied around gun regulation -- and even proudly held up a "disarm abusers" sign -- years before he shot his wife, and then himself, in an apparent murder-suicide ... TMZ has learned. Check out the photo -- the now-deceased politician is smiling alongside gun violence survivor Kate Ranta and her young son while posing with the pointed sign the minor made. You can see the sign's intentions loud and clear -- it's taking aim at the National Rifle