The problem is many people have the perception that in buying from a dealer, they are somehow 'protected' - from a legislative perspective, yes, this offers some further protection in comparison to a private sale, however in the real world, it's really the reputable dealerships and the big manufacturer-affiliated franchises that will be the least hassle to resolve problems with as they have more to lose - I would try to use the same caution buying a used car from a dealership as I would in a private sale. I'd rather ignore the pseudo-safety-blanket and avoid any hassle (especially something that could be stressful, time consuming and costly), right from the outset.
The perception of value is what will determine the purchase of goods or services. If someone is happy to pay for one of the cars there, and they feel it's a good buy whether its a pristine example or a bit tired, then I wish them all the best - however I would urge caution based on the consistency of the actual complaints in the negative reviews that place has received (the number of complaints will always be higher for a volume seller).