I have generally found that people who claim that their treatment will cure everyone should not be trusted. No competent health professional in any field would ever say their treatment helps everyone.
Even in the most positive EMDR studies, it does not help 100% of patients, Can he back-up this statement? is he getting this opinion from a randomised control trial or his own anecdotal experience which is tainted with small sample sizes, bias in so many ways, select patient groups - I could go on but you get my drift

I'm sure he has had good results with many patients - but these may have been uncomplicated, 'easy' problems. There is a whole new set of rules when someone has a complicated history of ineffective treatments