Firstly, you can't look at records from those days the same way. It was not uncommon for guys to have 100+ fights on their records. Especially in the lower weight classes, there wasn't nearly as much money in a single bout because the only way a fight made money was by putting butts in the seats, and boxers had to fight frequently in order to earn a living. As a result, they would sometimes fight bouts less than a week apart. Only the biggest fights allowed time for a proper training camp and most boxers stayed in shape and honed their skills by fighting constantly. This meant they often fought injured, malnourished, or exhausted, and usually a combination of all three. There was also a lot more travel involved. Boxers would go on tours of the country, fighting in a different state every week, subject to hometown decisions in favor of the local hero or just being too worn out to fight on. Sometimes they'd arrive in town only to have the planned bout fall through and they'd have to take fights against guys way outside of their weight class just to cover the expenses of their trip. Fighters who were once world-class and had devoted their lives to boxing would fight on long past their primes against younger, fresher men and see their records tail off towards the end of their career, many of them ending up punch-drunk and broke.

Robinson was like most fighters of his era; he started young and went up the weight classes as his body changed and he got older, starting his career as a featherweight. By the time he fought Randy Turpin in 1951, Robinson was 30 years old, had been fighting professionally for 11 years and was the lineal middleweight champion with a record of 128–1–2. His resume included wins over Fritzie Zivic, Sammy Angott, Jake LaMotta, Henry Armstrong, Artie Levine, and Kid Gavilan, all future Hall of Famers. At this point, Robinson was still arguably in his prime, having fought in multiple weight classes and now a dominant champion. He would notch wins over Randy Turpin in a revenge match after losing the first one, Bobo Olson, and Rocky Graziano before moving up to light-heavyweight against Joey Maxim. He would dominate that fight for 13 rounds before collapsing with exhaustion fighting a man who carried well over twenty pounds of additional weight. Now on the downside of his career, he would win and lose several more matches against Gene Fullmer, Carmen Basilio, Paul Pender, and Denny Moyer and a host of others. Every name on that list is a Hall of Famer, and that's just a casual inspection.

In his prime, he was an elite combination of power, speed, and technique and carried all of it with him up to middleweight. He fought the best of his era and usually won before age and wear and tear finally eroded his otherworldly abilities and brought him down to earth where average fighters began to catch up with and outpoint him. Through all that, the only knockout loss on his record was when he fell apart against Maxim. I think if you really look into the details of Robinson's career, he is unquestionably one of the best ever.