One thing not mentioned by others here is that many wives believe that a gun and/or ammunition is a complete waste of money. Unlike a purse bought for $250 and later sold for $40 or donated to the Salvation Army, a firearm can often be sold for the same or more than the cost when purchased. When held for more than a decade, firearms prices can actually rise above full retail purchase price. When explained as an investment, it takes on a different tone. If your spouse doesn't see the point, ask how many clothes in her closet, shoes or purses she has that can be sold for more than the purchase price? Don't be a d!ck about it, just gently point out that this money is not wasted and can be recovered if needed in an emergency. This will refute her belief that you are "wasting" money. This is also a good argument for a safe purchase, as a safe protects your investments, I.e. guns, gold, stock certificates, jewelry, etc. if you wish, you can also explain how much value you can add by purchasing used or building your own.
My first wife was a control freak who never wanted anything to do with guns, shooting or anything related...until the divorce, then she wanted half. My current wife is my best friend, an avid and very accomplished shooter, and we have all sorts of fun together! I won't tell anyone to get divorced, but I agree that life is too short to be tied to a controlling shrew. Do everything you can to help her understand your interests and enthusiasm, and consider trading a shooting session together for one of her interests that you have dodged before - antiquing, opera, quilt show or her Mother's house are all good! This will demonstrate to her how very important the sport and her acceptance of it are to you. "My way or the highway" is a recipe for confrontation and should be your last ditch tactic, as you have to be ready for the alternative. Compromise at first and you may find your spouse as interested in shooting as you are. :-)
“Malo periculosam, libertatem quam quietam servitutem." (I prefer the tumult of liberty to the quiet of servitude.). Thomas Jefferson
"All that is necessary for the triumph of evil is that good men do nothing."
-Edmund Burke, Loosely translated from Thoughts on the Cause of Present Discontents. (1770)