Unfortunately, I have had the same experience in my own country, Canada. The couple of times I've been in a potentially violent situation, the rent boy has been drug addict or mentally ill. I'm saying this because occasionally you will meet a desperate guy who needs the cash right away for their next fix. I don't think situations like that are unique to Colombia. Just look at the hideous Luca Magnotta case in Montreal who dismembered his victim and committed cannibalism.
Gay life has its hazards. Erring on the side of caution is the best policy. If they exist, staying at a gay B&B in Colombia might be a better choice. In the case of Cuba, the staff at Havana casa particular I stay at (Casa Arian) screen the boys for you.
Stay safe!!