On a serious note, I think you should give criticism where it is valid whether they can handle it or not. Otherwise they will be oblivious, and no-one benefits.
However there are instances where you should hold back, for instance if you are in a bikers bar, don’t criticise bikers as being idiotic for using one of the most dangerous modes of transport.
Also perhaps in instances where the person can’t achieve any positive change as a result of the criticism. (constructive criticism)