My parents used to bash the Trinity without ever knowing what the doctrine actually taught. They even convinced a few, (emphasis on 'few'), Catholics to join their church using the Watchtowers explanation of how the Trinity didn't make sense. If their converts had understood the definition in the Catholic Encyclopedia, they would have seen through the WT subterfuge that my parents had fallen for. If my parents had been properly taught what the doctrine was and how it was arrived at by their parents and grandparents and Sunday School teachers, they wouldn't have fallen for the WT scam either.
I'm not saying that the Catholic doctrine is correct, (I'm an atheist), but I do know how to debate their official doctrine with a JW.