For hauling heavy items, I would agree with a trailer. It is not just getting the bike up into the truck: backing it down is more frightening to me that riding up into the bed. Lots of potential engergy with that much mass, that high in there air. I think we have all had the forks through the bike over a bit if you are going backwards and grab the front brake too hard. On a ramp it is worse.
That said, many haul bikes in their pick-ups with minimal problems. I would recommend that if you have a receiver hitch, get some 1/4" wall x 2" steel square tube and weld up (or have someone weld) a "tee" that comes out of your hitch, 90's up toward the lowered tailgate and has a cross member that is level (or a 1/4" or so above) with the lowered tailgate. Add some supports from the ends of the cross member back to the tube coming out of the receiver and you will have very little "twist" from the triangles configuration.
This is cheaper than a trailer and most hitches are rated for at least 500 lbs. Add a some boards and you reduce the weight on the tailgate. Even the ramps mount to this support, not the tailgate. Add some eye-bolts and some tie downs and this is pretty solid, even on bumpy roads. Easy to install and comes in handy for trips to the hardware store.
I still say go for the trailer if you can, but I understand if you can't or don't want to. My neighbor tore his rotator cuff trying to save his bike from falling over, while backing it down the ramp. Ended his trip to Sturgis before it started.