Tire challenge - 15"

Was looking at fivers today, the Stealth we looked at had 15" tires, I told them no way I am going with 15" tires. Their answer was these tires (blow masters) are way better than those crapisles. I told them I went to 16" commercial truck tires on my current rig, their answer was you should not run LT tires on a trailer, the sidewalls are too stiff and you can pop the bead off the rim when backing too sharply because of the tire scrub. It took everything I had to not call the salesman an idiot. I won't be going back there for sure. If tire scrub could pull the bead off the rim, why don't those over the road flatbed trailers with the wide spaced axels do that ??
2 weeks ago, I was told I could easily pull a 12K dry triple axel rig with my 2500HD, It totally sucks trying to shop for a rig when you have to deal with idiots.