Can it be for certain that the hobbyist, regardless of "homework" done or not done, might have played a role in his own demise or even might have totally brought it on himself? OP seems to lay this on the provider, maybe I am taking it wrong.
From the posted link it appears like this was a typical upsell situation that occurs when gents evidently just close their eyes and point at a backpage ad without researching it. It is odd the two met before and it went down like this, but not unthinkable, at least that she changed the arrangement. I have read reviews of guys who were ripped off by providers they had seen before.
Who knows what prompted the man to pull the knife, that is what the woman claimed happened, I am sure they can investigate whether or not the knife was indeed the 61 year old's or not. I have sympathy for anyone who gets taken by some thief or upseller on backpage but if he drew the knife then he played a part in his own death, either know how to handle and control your weapon or just let the thief leave and chalk it up as a lessoned learned.
Hopefully the truth comes out. It could have been self defense very easily, hate to stick up for someone who probably was trying to hoodwink the guy but pulling a knife just was not a smart thing to do.
This shows that all the stuff about "human trafficking" on backpage is just a lot of BS for the most part, this sort of incident is what I seem to gather is more commonplace, "providers" and gangs of theives using it to steal and rob, than what they wail about trafficking.