but if it is a case of just going to close to a CB then they have no-one else to blame but themselves.
I have spent many dark and stormy nights flying through the ITCZ to and from South America. Many times we'd be cruising in a hazy layer and relying completely on wx radar for avoidance. Even with two experienced pilots actively scanning and tilting for CBs we still managed to get into very turbulent tops with lot's of St. Elmo's fire on a regular basis...not ever severe turbulence but definately more than you would expect from an area that was either not painting or only very lightly painting on the radar.
In tropical regions CBs and their associated turbulence are not always easy to detect and avoid. Until you actually spend some dark and dirty nights boucing around over the Pacific or the Amazon you don't really have an idea of what these guys may have been dealing with.