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.