The watchtower interpretation of the verse is not logical. The person that decides to leave or not join watchtower is 'unsuitable', but then if that same person decides to come back to watchtower he is then no longer 'unsuitable'- this means its the individual's choice whether to be unsuitable or not, but according to the text it was the fisherman's choice.
It's just another example of murdering a scripture to make it more 'suitable' for the cult.