I think CBT can be harmful for example when living with a narcissist or when the victim is being gaslighted. Running that problem through CBT will only maybe the victim feel like an idiot and he'll start doubting himself.
CBT in my opinion, only works in an ideal world. It denies any real issues as well as genuinely negative traits of the person (too positive thinking leading to being blind to one's negative character traits or lack of skills). It then leads to disappointment.
I think cbt is so rational that it's in fact irrational :-)