Yeah, but he's cheating! He's got a bag with backpack straps (I've got a stand bag like that...wonderful thing)! LOL.
I rarely take the bike to the golf course, but when I have, I lay them across the passenger portion of the seat and bungie them down by making a "X" across the bag. I've never had a problem. But DEFINITELY put the rain cover on the bag, for goodness sake!
One of my coworkers, who's an avid golfer, ride his bike with them on the back all the time. Of course, he's got a VTX 1300 with big old saddlebags, so there's something to stabilize the bag with.
It can easily be done. It's not something you want to go hitting the twisties with or lane-splitting with (for our Cali brothers and sisters), but it's not that hard to do.