A typical cliche of UBF defenders (and other cult members) when it comes to criticize their leaders ist "Don't judge." I heared it so often in the time of the reform movement (and of course, mostly with a judgemental undertone ;-). The following article is one of the best answers to that objection "Don't judge."
It says that in such cults people are not being taught to think, instead they are taught what to think. I think that is a very good summary of what makes UBF problematic; a place where you (after a certain point) will not grow as a Christian any more, but only degrade.