Is imitating Christians considered a major sin, like consuming alcohol and fornication, or is it worse, and does the imitator place himself in a position of disbelief (kufr)?

The ruling on imitating disbelievers varies; it can be disbelief (kufr), innovation (bid‘ah), a major sin (kabirah), or disliked (makruh), depending on the type of imitation. Sheikh Saleh Al-Fawzan was asked about some young people imitating disbelievers in their clothing, and he replied that imitation varies: some of it is disbelief (such as imitating them in worshipping the dead), some is innovation, some is a major sin, and some is disliked. In any case, imitating disbelievers is prohibited, based on the Prophet’s (peace and blessings be upon him) saying: “Whoever imitates a people is one of them.” It is considered a form of showing loyalty to them. It should be known that persisting in a sin transforms it into a major sin, even if it was originally a minor one. It has been stated: “There is no minor sin with persistence, and no major sin with seeking forgiveness.” And in the hadith: “Beware of minor sins, for they accumulate upon a person until they destroy him.”