Question:

“If someone imitates the Jews or Christians, do we say that he is a Jew or Christian based on the hadith? I hope for clarification.”

Al-‘Allâmah Sâlih al-Fawzân:

“We clarified this. Imitation can be shirk that is Kufr, it can be muharram (forbidden) and that is less than shirk and it can be makrooh (disliked).”

Source: http://www.alfawzan.af.org.sa/node/14823