It's true that Idealists are all about harmony, integration, unity. And, especially, the Conciliator Idealist.
"To the INFP, healing means mending those divisions that plague one's private life and one's relationships. It means treating oneself and relating to others in a conciliatory manner, helping to restore lost unity, integrity, or what INFPs call "oneness." These Healers present a tranquil and noticeably pleasant face to the world, but while to all apearances they might seem gentle and easy-going, on the inside they are anything but serene, having a capacity for caring not usually found in other types. Healers care deeply--passionately--about a few special persons or a favorite cause, and their fervent aim is to bring peace to the world and wholeness to themselves and their loved ones." *
But the Healer is all about purity too. In Portraits of Temperament it is said that "their totem deity is Hygia, god of Health, after whom they seem to have fashioned themselves....some must atone for...evil they have been taught to believe is in them, must somehow sacrifice. With this project of undoing comes a certain fascination with the problem (peculiar to introverted Healers) of good and evil, sacred and profane, pure and sullied, virginal and pregnant. They are drawn toward purity, but they continuously look over their shoulder for the violation that stalks them." ^
Also, they "hear a calling to go forth into the world to help others, and they seem ready to make the personal sacrifices involved in responding to that call, even if it means asking their loved ones to do likewise....This almost preconcious conviction that pleasure must be paid for with pain can cause a sense of uneasiness in INFPs when they marry; they may feel they must be ever-vigilant against invasion, and can therefore have trouble relaxing in the happiness of mating." ^^
So, with all this in mind, I make this comment: it is possible for an Idealist, and especially a Conciliator, to do what Hitler did, if he saw the Jews and others as a "plague" that caused "divisions," and purity as a means to unity. He would passionately defend his ideals against "invasion," his "fervent aim to bring peace to the world and wholeness to loved ones," and being willing to "make personal sacrifices and asking loved ones to do likewise." 'Yes, we have to rid the world of many undesirables, but this is all for the good of humanity! These sacrifices must be made, in the name of what is good.'
*(Please Understand Me II, page 157-158)
^ page 110
^^Please Understand Me II, page 160