I believe saying "Vajrayana" is inappropriate for people with mental-emotional disorders is simply uninformed and wrong. While it is true that doing Vajrayana practices wrong can cause mental-emotional problems, that is not a problem with the system but a problem with a particular individual doing a particular practice wrong. Such wrong practice may be do to not having a personal Teacher to choose the appropriate practice and/or to explain how to do the practice correctly. It may also be due to disregarding one's Teacher's instructions. As has been stressed on this forum many times before, there is no "real" (i.e., safe and effective) Vajrayana practice without a Teacher. A bona fide Teacher should be able to assess a given student/patient's condition and then recommend the appropriate practices to remedy that/those conditions. In point of fact, there are plenty of Vajrayana practices specifically capable of remedying psychiatric disorders. As an example of this, take Chogyal Namkhai Norbu's Uncle Togden. In his biography, it clearly states that Uncle Togden was very definitely psychiatrically disturbed at the time he went to Adzom Drukpa and that Adzom Drukpa gave him specific practices to do for his condition. Not only did these practices "cure" his psychiatric condition but Uncle Togden eventually achieved the Rainbow Body.
It seems to me that the key here is not the system as such but the ability of the Teacher to chose the right practices for the right student and give adequate instruction in those practices. That makes finding the right Teacher all the more important for a student with a serious mental-emotional disorder. This includes the Teacher's ability to assess the student as well His or Her ability to appropriately monitor the student's condition, making changes and suggestions in a timely manner as needed. In other words, one needs a very wise, experienced, and available Teacher.
Pema Chophel པདྨ་ཆོས་འཕེལ