Tom, if it were me, I would go back to the store and complain about the rub and make them make it right.
When I upgraded from Cooper 285s to the Duratac 315s, we moved the tire left and right via full steering wheel turn and made observations. We had a 315 rolled up to the vehicle and made observations.
If Discount Tire did less, I think the onus is on them to make it right. They're the experts and in the position to sell you the right parts. Especially at this price. As a retailer they have a district manager and a corporate number you can call.
I seriously doubt they want to have an irate customer in their store in front of other customers complaining that they made a bad decision and are not resolving the issue. By asking the manager to walk with you to your vehicle to discuss this, you can reiterate this leverage and just flat out tell him he needs to swap those tires for another brand or size that fits. That much as has control over.
Oh and BTW - if they offered you a rebate for this purchase, know in advance that this scam rebate card actually expires in a few months, hoping you won't get around to using it.