I think it would depend on what horrible means. If it means that one is a sinner, then all are horrible (including unborns).
However, if horrible means what I think it is, then no true Christians are horrible. There are false Christians, just as there are false unicorns, so it depends on how one reaches the conclusion, I believe. The definition of a Christian is one that has been saved by God. The true Christian may sin, but they are not going to do horrible things. It, the Bible, even said that Lucifer would be able to deceive even the elect, WERE IT NOT for the Lord.
By "TRUE" they meant real Christians. They were not changing the definition. A Scotsman is defined by his place of birth or whatever, but defining a Christian is extremely difficult, since you do not truly know who is saved and who isn't, no matter what one may say. They bear fruit, however, and that helps oh-so-much.
Yes, if those men were true Christians, that was very wrong of them, as they are following after the Inquisition: destroy heretics. Instead of yelling at you, they should have acted like Christ, and shown you good reasoning.
The Bible states that no true Christian will continue living the way he did—he will be a new man, and try to cast off sin. Therefore, you have made a fallacy yourself. Of course, he wouldn't be perfect, but he would do everything in his power to escape the sin, and run into Jesus' arms.
It MAY be, as in that example, that ONLY a 'true unicorn' has 'curves'. You have made a fallacy yourself. Perhaps identify it in this case: "OF COURSE he's going to say ONLY good men can be Christians because HE'S a Christian!"
Do not cling to folly, my friend. It is foolhardy. You have no right to say whether or not true Christians are only in the good man or woman, since you yourself probably don't know much about true theology.
