Eh Cus grew up having to defend himself in knife fights. If that kinda shit doesnt turn you into a crook at a young age. I dont know what does.
Knife fights, as in more than one?
Or are you meaning some story that Cus liked to tell about an alleged knife fight that didn't even happen because, according to his telling (and it's only his telling as he claims there were no witnesses to it...he may have came up with that one in some book, or from his head, just like he did with some of his other inspirational stories he was known to tell), the other guy didn't show up for it?
Even if true, though, and speaking from personal experience (looks down at four inch scar on right forearm by the elbow*), it isn't all that uncommon for someone to have defend themselves against knives, other sharp objects (my scar's from a broken beer bottle), or any other type of weapon, and while I may be a dick at times on here, I guarantee you that I ain't a crook and never have been.
But anyways, you could say that Cus learned to be a crook in boxing by working for, and then later with, other crooks in the sport at the time, and that makes sense, and also may make it understandable why he did some of the things he did. But I think it's quite hypocritical how he's portrayed as some "honest" man in today's age just because he ended up having some grudge against the crooks (that he worked for, I might add, and continued to do business with even though he publicly stated he was against doing so) who were pretty much running the show at the time, and meanwhile he's doing the exact same type of business with other mob figures and shady characters who weren't associated with that organization.