My dad owns a security company and still has tons of guns
He is a very responsible gun owner (like most people are who are very into their weapons). A security system is great, but if someone is determined enough to come in and kill you, having a gun can't do anything but help yourself more. A security system is a wonderful thing to have in a house, in that it will wake you up, should you be sleeping during an intrusion, it will deter thieves, it will alert police, and protect your house when you're not there.
Why not have a second layer of protection? Much like I take the steps to ensure my dog will get back to me if ever loose... he wears tags, he's microchipped, etc, etc... just all added layers of protection. Using a gun should be a last resort. A home security system would hopefully stop you from even having to use one and hopefully stop or deter criminals from actually entering your house. But there is nothing wrong with responsibly keeping guns in your house, unloaded, locked up, and a person who is professionally trained how to use one.